Dressed in blue jeans and a checked shirt, Maggie Gyllenhaal toys with her BlackBerry as she keeps track of her baby daughter’s needs. Lit by natural light from a window at New York’s trendy Maritime Hotel, she appears to hide the vulnerability that she displays so successfully on screen. As we talk, however, I notice a softness to her voice. Her milky blue eyes look innocent. It is subtle traits like these that are magnified by the movie camera and can make a rising star.

Gyllenhaal’s new film, Sherrybaby, was inspired by the true story of a drug addict named Sue, a high-school friend of the first-time feature director Laurie Collyer. Sue went to prison the same year that Collyer graduated from college. Collyer became so obsessed with Sue’s fate that she spent years working on a script about her, with help from the Sundance Filmmakers Lab. The film, shot in a gritty documentary style, is dedicated to her.

Collyer chose Gyllenhaal, fresh from her breakthrough success in the sadomasochistic romance Secretary, for the part because she considers her the most exciting actress of her generation. But a strange thing happened when Gyllenhaal began researching the role. Although she visited jails and talked to ex-convicts, she refused to meet Sue. “[Collyer] can think the film is about whoever she wants,” Gyllenhaal explains. “She kept giving me videos to watch and I sort of said, ‘Great, well, thanks, but . . .’ Sherry has to come from me. Otherwise it’s an imitation of someone.”

The 29-year-old actress owes her confidence perhaps to the fact that she comes from a film family. She made her first screen appearances in films directed by her father Stephen. Her mother Naomi is a screenwriter. Her fiancé, Peter Sarsgaard, is a Golden Globe nominee who appeared in Boys Don’t Cry. And, of course, her younger brother Jake won acclaim playing a gay cowboy in Brokeback Mountain.

BACKGROUND

• Sherrybaby

• She's no wallflower

A star and ‘momma-lion’

As the actress Maggie Gyllenhaal’s star continues to rise, she is fighting to protect her family’s privacy

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Gyllenhaal has mixed appearances in indie films such as John Sayles’s Casa de los Babys and John Waters’s Cecil B. Demented with bigger budget projects such as Oliver Stone’s World Trade Center, where she played the wife of a Port Authority police officer buried in the rubble of the twin towers. After completing the low-budget Sherrybaby, she is now shooting the new Batman movie, replacing Katie Holmes as the Caped Crusader’s romantic interest.

Brought up in Los Angeles, Gyllenhaal was educated at Columbia University in New York, where she majored in English literature and studied Eastern religions with Uma Thurman’s professor father Robert. She readily admits that she has little experience of the world of suburban heroin addicts in which Sherrybaby is set. “I’ve never seen anybody shoot up heroin. I’ve been around people who snorted it,” she says.

But Collyer’s heartfelt script about her friend tugged at her. The film follows the Sue character, renamed Sherry, as she tries to retrieve her relationship with her young daughter after three years in prison. The story is downbeat but Gyllenhaal’s performance brings a sparkle to the film. It earned her a Golden Globe nomination.

“There are so few movies made about people like Sherry . . . that actually just honour them. That is what I wanted to do – to honour her,” she says.

Gyllenhaal plays the parolee as full of childish wonder at the outside world, after years on the inside. Although she is a recovering smack addict, she becomes a sunny presence on screen. Her portrayal seems in conflict with the darker vision of the director. Gyllenhaal admits that they “fought like crazy” during the 25-day shoot. “When I was so hopeful and looking for pleasure everywhere, Laurie was really shocked. And I just said, ‘You’re wrong.’ ” Gyllenhaal says that Sherrybaby sucked her in. “Although it’s a 25-day shoot, which is nothing, I was involved in getting the financing, doing the shooting, seeing all the edits,” she says. “Then [I was] involved in getting it into festivals, finding a distributor, helping with distribution, helping with the press. It’s almost like being a producer.”

Sometimes, though, it is a relief just to be an actress, she says. Her current role in Batman sequel The Dark Knight has surprised her. She calls Chris Nolan “a really great director”. “He made suggestions and pushed me in ways I just didn’t expect on Batman,” she says.

Gyllenhaal performed full-frontal nudity in Secretary. Sherrybaby has plenty of sex, although it does not quite go that far. But Gyllenhaal’s breasts have recently stirred controversy. On a visit to Central Park in New York, Gyllenhaal was photographed breast-feeding her baby Ramona. The pictures were posted on several blogs, stirring debate about breast-feeding in public.

Eyes flashing, Gyllenhaal says that the paparazzi are out of control: “I do not want my daughter in any of those magazines. I get a momma-lion feeling about her having her picture taken. I think it’s disrespectful to take a picture of a nursing mother and it’s inappropriate to put it on the internet. If you want to go outside with your hungry child, you have to feed your child.”

— Sherrybaby is out on July 27

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