Nora Ephron: Screenwriter and author who became the doyenne of Hollywood romantic comedies

Ephron in 1978 with her second husband, Carl Bernstein, whose infidelities inspired 'Heartburn' (AP)

Screenwriters are the hidden stars of the film world, credited only by name and seldom fully recognised for their work behind the scenes. Nora Ephron was a master of romantic comedy and one of the best screenwriters of her generation, who broke into a world that had previously been dominated by men. As the author of scripts for 15 films, it was her use of humour and observations based on real life - often her own - which so enchanted cinema audiences. Three of her films were nominated for Oscars: Silkwood, When Harry Met Sally and Sleepless in Seattle.

Nora Ephron was born in New York City in 1941 to a show business family. Her parents, Henry and Phoebe Ephron, were Hollywood screenwriters whose writing credits included the film adaptation of Carousel (1956) and There's No Business Like Show Business (1961). She was the oldest of four sisters, all of whom went on to be involved in writing.

She graduated from the women-only Wellesley College in 1962 and, seeking a role in journalism, started as a mail girl at Newsweek magazine. Talking to an audience at the college in 1996 about her first workplace, she recalled, "We weren't meant to have careers that mattered, or opinions, or lives; we were meant to marry them."

Her break into journalism came when she was asked to write a parody column for the New York Pest, a spoof newspaper conceived by Victor Navasky. She rose to the task and the result so impressed the editor of the real New York Post that she was offered a job, lasting for the next five years. While at the Post she began freelancing for the New York Times Magazine and for Esquire, for which she went on to write a regular column.

Ephron's first screenwriting role was on Silkwood (1983), co-written with her friend Alice Arlen. This daring and controversial début, starring Meryl Streep and Kurt Russell, was based on the life of Karen Silkwood, a nuclear lab technician turned whistleblower who died in mysterious circumstances. Vincent Canby in the New York Times remarked admiringly, "Perhaps for the first time in a popular movie has America's petrochemical-nuclear landscape been dramatized, and with such anger and compassion."

The film's director, Mike Nichols, said of this time: "I think that was the beginning of her openly falling in love with the movies ... she and Alice came along with Silkwood when I hadn't made a movie in seven years."

Three years later Heartburn (1986), based on her own novel, was inspired by Ephron's troubled relationship with her second husband, the journalist Carl Bernstein. The movie tells the story of Rachel Samstat (played by Meryl Streep), who discovers that Mark Forman (played by Jack Nicholson) is having an affair. The philandering husband is notably described in the novel as "capable of having sex with a Venetian blind". A Rolling Stone review said: "Heartburn contains everything that is best about Ephron's writing: her urbane edge, her militant domesticity, her taste for revenge."

While with Bernstein, Ephron discovered the identity of "Deep Throat", the FBI agent Mark Felt who was the source for information on Watergate passed to her husband. Following their break-up in 1980 she revealed Felt's name to the media, having inferred it from clues left by Bernstein.

Her best-known script is probably When Harry Met Sally (1989), the romantic comedy starring Meg Ryan and Billy Crystal. Ephron based elements of the story on interviews with the film's director, Rob Reiner, who had just been through a divorce, together with anecdotes told by her own circle of friends. The film poses the question "Can men and women ever just be friends?" and ends with the answer, as the protagonists plan their wedding. Rolling Stone called it "a ravishing, romantic lark brimming over with style, intelligence and flashing wit."

Four years later she worked with her sister Delia on Sleepless in Seattle (1993), which became a box-office hit and further established her name as one of Hollywood's top rom-com writers. The film's two leads, Meg Ryan and Tom Hanks, went on to co-star in You've Got Mail (1998), one of the first films to use the internet and email as props, in a clever modern reworking of The Shop Around the Corner (1939) by Ernst Lubitsch.

A review in Variety observed: "Nora and Delia Ephron's script keeps some of the salient elements of the Lubitsch-Raphaelson version, but adds some commendable new ones. Most pointedly, the writers provide very good reasons for the friction between the two lead characters. There's a genuine professional rivalry between Joe and Kathleen, as his store threatens to put hers out of business."

Ephron's last film – as writer, director and producer – was Julie and Julia (2009), a culinary comedy in which Julie Powell sets out to make all the recipes from the first cookbook written by Julia Child. Liz Hoggard noted in this newspaper: "The success of Nora Ephron's film lies in the wonderfully nuanced relationship between Meryl Streep's 6ft, deep-voiced matron and teeny, balding Stanley Tucci. It breaks your heart to see two eccentrics finally find each other."

In two essay collections, I Feel Bad About My Neck: And Other Thoughts on Being a Woman (2006) and I Remember Nothing and other Reflections (2010), Ephron shared her observations on life and on the process of growing old, with wisdom such as: "As you age, live life to the fullest – travel to exotic places, eat good food, walk in the park, read lots of books and under no circumstances eat egg-white omelettes."

Tom Hanks and Rita Wilson said in tribute to their friend, who died of pneumonia as a complication of the leukaemia with which she was disgnosed in 2006: "Nora Ephron who knew what was important to know: how things worked, what was worthwhile, who was fascinating and why. At a dinner table and on a film set she lifted us all with wisdom and wit mixed with love for us and love for life."

Marcus Williamson

Nora Ephron, screenwriter and journalist: born New York City 19 May 1941; married 1967 Dan Greenburg (divorced 1976), 1976 Carl Bernstein (divorced 1980; two children), 1987 Nicholas Pileggi; died New York City 26 June 2012.