L'Wren Scott: Model who became a stylist and then an acclaimed fashion designer and was the long-term girlfriend of Mick Jagger

Scott with Sir Mick Jagger at a film premiere in London in 2007 (EPA)

L'Wren Scott was a fashion designer whose client list included Penelope Cruz, Angelina Jolie, Nicole Kidman and Naomi Campbell. Her trademark "Headmistress dress" had been sported by Madonna and remained one of her favourite designs, changing subtlely in each collection since its debut in 2006. Although she was a private person, her approach to work was characterised by the need for a reaction, whether positive or negative, to her designs. As she said, "It is always interesting if someone either loves or hates it – if there's no grey area, that means 'job well done'."

She was the partner of the Rolling Stones frontman Mick Jagger, who she first met in 2001 at a photoshoot. The pair were first seen in public at the 2005 Golden Globes awards ceremony, where Jagger jokingly thanked the 6ft 3in Scott "for not wearing heels".

Scott was born Laura Bambrough, and grew up in Roy, Utah, the adopted daughter of Ivan and Lula, who worked in a DIY store and bank respectively. The family were strict Mormons, and life centred round the church. But by the age of 12 Laura, or Luann, as her family called her, was already six feet tall and experimenting with fashion, buying a pair of flesh-coloured jazz shoes. Her mother did not approve.

Scott's stature prompted her to make her own clothes (she credited her family with instilling her work ethic). "I had to learn to sew when I was growing up, because nothing else fitted me", she recalled, "I used to spend hours at the local store, leafing through big books of Vogue and Butterick patterns, and then order one of them, and wait for it to arrive, so that by the time it was delivered I was really excited."

In 1985 she was spotted by the fashion photographer Bruce Weber while skiing in Utah and was invited to take part in a photoshoot for Calvin Klein. Although little-travelled and unable to speak French, she bought a one-way ticket to Paris, where she modelled in shoots for Chanel and Thierry Mugler. In 1992 she starred in the memorable Pretty Polly "clock" advertising campaign, directed and shot by David Bailey, in which her legs tick around the clockface to the tune of "All Day And All Of The Night" by the Kinks.

Scott's fascination for fashion next took her to Hollywood, initially in public relations for Prada, then as a stylist for actors including Sarah Jessica Parker and Sharon Stone. In this star-studded world she was admired for her passion in styling, as much as for the discretion with which she dealt with her clients.

She also worked on clothing for her partner Mick Jagger, but emphasised, "I'm a fashion designer. I don't want to be defined as someone's girlfriend," adding, "You always wonder if people will pay attention to the hard work that goes into what you do. And when you're taking on something on your own, it's your company, your investment – your life."

In 2006 she fulfilled a lifelong ambition by creating her own label collection, titled Little Black Dress, which included her now famous "Headmistress dress". She said that she had always struggled to find the perfect black dress and so had to create her own. Combining a figure-hugging pencil skirt design in black fabric, with a white collar, and often a white bib, the design became synonymous with the L'Wren Scott name.

She had recently collaborated with the high street chain, Banana Republic, to introduce a range of clothes and fashion accessories for those on more modest budgets. Scott had also worked on costume design for films including Eyes Wide Shut (1999) and Ocean's Thirteen (2007). Ellen Barkin, who starred in Ocean's Thirteen, said of her creations, "If I looked naked like I look in her dresses, I'd be happy."

Scott was an art collector and derived inspiration from the work of the artists she loved. Her most recent collection, from last September, was influenced by the aesthetic, colours and life of Gustav Klimt. "His process and journey and evolution. I loved reading about his love affair with Adele Bauer", she said after the launch show, "I guess I was just ready to sparkle... I wanted to see the girl walk out of the picture." As a Vogue reviewer wrote, "It was disco, it was Seventies and it was rock 'n' roll all in one – her woman has the Midas touch and glitters in gold."

Scott was found by her assistant on the morning of 17 March at her apartment on 11th Avenue, Manhattan. New York police said they were investigating the death as a suicide; there had been reports that she had been suffering financial difficulties. Jagger was with the Stones touring Australia and New Zealand, but the day after Scott's death the tour was cancelled.

Anna Wintour, the Editor-in-Chief of Vogue, paid tribute to Scott, saying "L'Wren was a total perfectionist, someone who absolutely embodied everything her marvellous clothes stood for: strength of character combined with a confident and powerful style. In person, L'Wren was always unbelievably generous, gracious, kind, and so much fun. Her old world American manners and charm were from another time, but her sensibility was always fiercely modern."

Laura Bambrough (L'Wren Scott), fashion designer and model: born Utah 28 April 1964; married 1993 Anthony Brand (divorced 1996); partner to Mick Jagger since 2001; died New York 17 March 2014.