Blue planet: Dakota Blue Richards on the trouble with being a teenage film star

Dakota Blue Richards is the seasoned film actress who stars in Warner Brothers' latest big-budget fantasy, 'The Secret of Moonacre'. Whether she's working the red carpet, on set with Nicole Kidman, or dealing with scandalous headlines, she knows just how to handle herself. But what kind of world is this for a 14-year-old girl from Sussex?

At first glance, I barely recognise the new Dakota Blue Richards. Gone is the fierce little girl with soft auburn hair who played Lyra in The Golden Compass, the 2007 adaptation of the Philip Pullman novel. Here instead, at 14, is an extremely self-possessed mini-starlet, with kohl-ringed eyes, a swanlike neck and artificially dark hair, ornamented with tufts of black faux fur. And check out those high heels! She can walk pretty well in them, too. I feel a pang of loss that her unspoiled younger self has gone so soon. But isn't that just the way with child stars? We over-invest.

I meet her at the Sunday morning children's charity premiere of her latest film, The Secret of Moonacre. The mini-celebrities are out in force, working the red carpet. The thimble-sized EastEnders actor Devon Higgs is posing with Charlie Wernham, the 13-year-old stand-up from Britain's Got Talent. Beside them, beaming shyly in a tutu and wellies is the actress Maisie Smith, only eight but already cornering the market in redheads, having played both the young Elizabeth I and Patsy Palmer's daughter. The press shout at them appreciatively. Then Dakota arrives and they go mad.

"Dakota, over here!"

"Smile for me, Dakota?"

"On your right, Dakota!"

The fans, too:

"Would you sign my programme?"

"I've been wanting to meet you for sooo long!"

And the TV news crews: "What's the best thing about being Dakota Blue Richards?" Then she has to give three speeches introducing her film to three different screens inside the cinema, then there's a bundle of charity posters that need signing, and finally, there's the woman from the Independent on Sunday waiting to speak to her. She sits down opposite me looking like she might cry.

"I'm SO annoyed. All my friends are in there, watching my film. And I've had to come out and do interviews."

Wow. She's got the teenage voice and attitude to go with her new look. She doesn't come across as rude, just heartfelt. And while in an ideal world the child starlet should be able to watch movies as well as perform in them, in reality it's impossible as she has only one day, today, to promote her huge-budget Warner Brothers film, due to the claim on her time by the small legal requirement known as school.

How many friends does she have with her today? Seven. Boys and girls? Yeah. Friends from school or friends from films? This provokes another gust of exasperation. "People just don't understand! I don't hang out with people like that at the weekend. I know people from working with them on films but they're not the ones I would meet up with... I'm just a normal person!"

Ah yes, the "normal" word. When I interviewed the Charlie and the Chocolate Factory star Freddie Highmore in 2007 he also used it with touching frequency, about himself, his hopes for the future, even, most improbably, about his co-star Johnny Depp. Dakota says working with Natascha McElhone was really lovely because, "It's nice to have normal people around." You can see why child stars like the normal word – it's modest, conservative, self-defensive, a good way of saying something without saying anything – but really, what normal person would ever describe themself that way?

Dakota Blue Richards was not christened for normality. Her mother Mickey (short for Michaela) – a calm, watchful presence at the premiere – chose it after spending some time in the US near the Dakotas with the Sioux tribe of native Americans; she had wanted to name her for a place and a colour, and she has said that Dakota's absent father (not named on her birth certificate) was nicknamed Blue. Mother and daughter live outside Brighton, where Mickey runs a drug treatment centre and Dakota – "Dee" to friends – went to an independent school until 11, when she moved to K-Bis, a stage school.

Her life changed when she went along to the open audition for the part of Lyra in The Golden Compass and was chosen out of 10,000 girls. The stories about that magic day are well-rehearsed (she's even told them on the Ellen Degeneres Show): her mother was going to take her along only if she promised not to be disappointed if she didn't win, and if it didn't rain. She didn't brush her hair that morning so she looked "untamed" – like Lyra. The film's director, Chris Weitz, later praised her "intelligence combined with a feral quality".

Gabor Csupo, who directed Moonacre and has worked with a lot of child actors, told me she was a star in the making. "She's very withheld with her emotions, but you can still read a huge range of feeling in her eyes. I really respect that type of performance, that minimal expression." He says she was very good at interacting with a red laser dot and pretending it was a lion. "You know, she hasn't even been doing this for a long time, unlike some people who are acting from the age of five."

The Golden Compass was made on the understanding that, as with the Harry Potter franchise, they would be filming the whole of Philip Pullman's His Dark Materials trilogy. But The Golden Compass had a lukewarm critical reception and irritated the evangelical Christian lobby, and the whole project seems to have ground to a halt. "People say, 'Oh yeah I'd love to do that,'" says Dakota. "And 'We should do that,' and 'We should get this or that scriptwriter' but as far as I can see nobody actually DOES anything."

Has it been a disappointment? "Erm, a little bit? As I know the film was a big success. It was, like, the 109th biggest-grossing film ever made. I do worry the time will come when I'll be 16 and too old for it and they'll say, 'We're gonna get somebody else." Her little face looks, momentarily, very sad. But she keeps it together. "Which is a shame, as I loved the second and third books – if possible, more than the first."

Following her Christmas success in the lead role of Dustbin Baby, a made-for-TV film that delves into the fragmented past of an orphan, her new film, The Secret of Moonacre, is a lavish version of The Little White Horse, the children's novel by Elizabeth Goudge that was published in 1946. A sort of sub-Narnia for girls, it's a comfortingly old-fashioned fairytale film that Warner Bros is pushing hard ("it's getting the same publicity budget as [Oscar hopeful The Curious Case of] Benjamin Button," I overhear in the cinema lobby). It is not part of a series, although Dakota does have a suggestion. She thinks her character, Maria Merryweather, has hidden depths. "I think if there were to be a sequel or something, there would definitely be a lot more to learn about her."

In some ways, this young woman operates far beyond her years. For the three months she spent in Hungary filming Moonacre, there was one other young person on set: her stand-in (someone roughly the same size and height who stands in the star's spot while the crew are setting up, checking the light and so on) – but she didn't speak any English.

Dakota still had fun, befriending the DOP (Director of Photography) and eating most of her meals with the cast and crew rather than in her trailer: "The only time I eat alone is if I'm really tired or upset about something or on the phone to one of my friends, when it's easier to be alone. But you can't be too wrapped up in yourself ... it starts making you look a little bit prima donna. You've got to treat it like starting a new school. Just go in there and be confident from the beginning and say, 'Hi, I'm Dakota, do you mind if I sit with you?'"

She also made friends with a fellow actor in his early twenties called Augustus Prew, who plays Robin. Her line, addressed to him and his gang – "I know who you are, you're vagabonds and plunderers!" – became a bit of a catchphrase on set. In the first draft of the script, her character fell in love with Robin and there was a big kiss scene at the end. But that was never filmed, she says, her voice heavy with sarcasm, "which was quite convenient? Seeing as he's six years older than me." Kissing – gross! But later when I saw Prew at the premiere – all skinny tie and skinny jeans, perfect girl-crush material – I could also see why she might be suggesting a sequel.

"You grow up a lot on set," she says, "but it doesn't change you." Has filming made her more self-conscious about her looks? "Yes. I got into this at an age where I was never self-conscious about the way I looked, but going into make-up every day, well, it's fun, but it puts you into a frame of mind where you think, maybe unconsciously, why do I need it? Is there something wrong with me?" When she got the part in The Golden Compass she was asked if she would be willing to wear veneers on her teeth – she and her mother were horrified: "Like, what the hell?" She didn't have to, in the end, and "Generally, none of it had much effect on me, because I don't have low self-esteem.

"I'm a fairly confident person. It's not like I'm always thinking, 'Ugh, I look really ugly.' My mum says you should use make-up to enhance your good looks and that the make-up I wear is only to make me look even nicer. So it's nice having my mum there to keep me grounded." Her mother is her official chaperone on set, and her grandmother sometimes takes turns, too. Dakota doesn't worry about her weight either. "I can eat nothing or like a pig and it makes no difference because I have a really high metabolism. I think there's a really mature side of me that can deal with problems – but when I'm with my friends, I get to act much more kidlike."

Ah yes. Last year certain kidlike behaviour caused the scandal we shall refer to as "Snowman-gate". Provoking headlines including "Dakota Blue Richards Branded a 'Yob' by Locals," it was reported by the Telegraph and a local paper among others that the then-13-year-old actor had been "involved in the destruction of two snow sculptures" outside a newsagent in Hove. The girl and her "gang" had wantonly flattened a snowman and a snowdog – which had lumps of coal for eyes, no less. Abe Resteto, 40, a newsagent who joined with other community members to build the "sculptures", said, "We put our heart and soul into that snowman." Another local commented: "It seems kids today can't stop being inconsiderate yobs even if they are film stars."

A trenchant piece of news journalism, no? Dakota rolls her eyes. "It was a bunch of older guys who should have known better." The destruction, it seems, was provoked: "It was like, 'Throw ice at us and we'll kick down your snowman.'" Thinking about it, her instantly legible face darkens. "I reckon it was a bit of a set-up, really. I'm not cross, but you do just wonder what must go through people's heads when they think, 'I'm going to go tell that story.'"

Last year, her personal pictures were filched and disseminated online. "I can't have Bebo or MySpace or Facebook [profiles]," she sighs, "because there's fake people and fake finders saying, 'You're a fake unless you go on webcam to me.'" Later I browse online and find a YouTube film warning fans off seven different fake personal profiles for her. They have names like "Dee" and "BabyBlue" and feature strange modified pictures of her face, superimposed on to other young girls' bodies. On another site someone has written: "She goes to my school... she's sooo mean." Is it a fellow K-Bis student seething with jealousy? Or a weird old man typing nonsense? It's a scary cyberworld out there. After looking at those transmogrified pictures of her, I actually have a nightmare about them.

Usefully, Dakota's a philosophical kind of person. She's agnostic, she says, but "open to the concept of religion"; when filming wrapped she and her mother gave cast and crew ethical presents from the Good Gifts guide. When I ask if she feels under pressure carrying a film, she says no: "I don't worry because... have you ever heard the starfish story?" She tells me how saving the life of just one washed-up starfish on a beach of thousands still counts. "If you just make a tiny difference to one boy or girl, then you've won."

With that she's ready to rush off into the cinema, as fast as those high heels (not allowed for school) will carry her. "Next time I'm going to put it in my rider – must watch her own film!" she cries. "Dakota Blue Richards must have blue-berries two centimeters wide! And must drink Fijian water!" "Must drink tap water," her mother says, reprovingly, before adding, for my benefit: "And you don't have a rider, do you?"

Later, after the screening finishes, I watch families pouring out of the cinema. There are plenty of girls Dakota's age, faces dazed by the film and the excitement of the day, clomping awkwardly along in strappy sandals, patent boots, wedges and modish tie-up spats with huge heels. Babies, look at you now.

The Secret of Moonacre (U) is on general release