Rooney Mara: The girl with the dragon inside

Even now, more than a year and a half after Rooney Mara played her, it's impossible not to look at Mara and think of Lisbeth Salander. Yes, there are no dragon tattoos, piercings or leather-wear, but Mara and Stieg Larsson's hacker heroine from his Millennium novels seem cut from the same cloth. Today, her dark hair tied in a tight bun, Mara is warily processing every word. “I'm a very shy, private person,” she says. The phrase “handle with care” springs to mind.

Since twice working for David Fincher – briefly on his Facebook film The Social Network then extensively as Salander in an Oscar-nominated turn in The Girl with the Dragon Tattoo – Mara has rocketed onto just about every director's wish-list.

Acclaimed auteurs Spike Jonze and Terrence Malick have both recruited her for upcoming films, while she gave an engaging turn as a meds-taking Manhattan murderess in Steven Soderbergh's thriller Side Effects earlier this year.

She admits she hadn't planned on doing so many movies back-to-back – just Side Effects and the untitled, under-wraps Malick, co-starring Ryan Gosling and Christian Bale and rumoured to be set in the Austin music scene. But then came Jonze's new sci-fi romance Her – in which she plays Joaquin Phoenix's ex. “I couldn't say 'no' to it,” she says, “because I loved it so much.” Same goes for her latest film, Ain't Them Bodies Saints, which followed Her. “It jumped out at me. It had a very unique voice to it.”

Written and directed by first-timer David Lowery, it tells of Texas outlaw Bob Muldoon (Casey Affleck) who escapes jail and wants to reunite with his wife Ruth (Mara) and the daughter he's never met. It's not, she says, your typical lovers-on-the-lam tale. “Our movie picks up where Bonnie and Clyde or Badlands ends. It's seeing what happens after that part of the story. And our movie is certainly much less action-packed than Bonnie and Clyde. It's a quieter, slower film than that.”

You might say it's almost the perfect reflection of the 28 year-old Mara, who, living primarily in New York, shies away from the Hollywood circus. “I don't think of myself as a celebrity,” she says. “I don't feel like a celebrity in my life. My life hasn't changed that much.” So you can still go to the supermarket? She nods. “I go to the supermarket all the time, in my pyjamas! I'm just like a regular person – I go to the gym, I go to the supermarket, I go to the movies.”

While it's not clear what kind of regular person shops for groceries in their night attire, you get the picture. For the past three years, she's dated aspiring filmmaker Charlie McDowell, son of actors Malcolm McDowell and Mary Steenburgen, though they're both still low-key enough to avoid too much intrusion. “I like my anonymity,” she says. “I like to walk around alone, and get lost in my thoughts and observe other people. It would be a shame to not be able to do that, to not be able to be invisible and observe others.”

Born and raised in Bedford, New York, this disappearing act was always easy growing up – with an extended family that included 22 aunts and uncles and 40 cousins. Football, American style, is in her blood. Her mother Kathleen is a descendant of Art Rooney Snr, founder of the Pittsburgh Steelers. Not to be outdone, her great-grandfather founded the New York Giants – where her father, Timothy, now works. It hardly computes that this frail, pale, bird-like girl owes her upbringing to the macho world of NFL.

She tells me she “was not a performer” growing up. She was, for a time, in the shadow of older sister Kate, who also acts, recently starring in Fincher's Netflix series House of Cards. Would they consider making a movie together? “We would love to work together but it'd have to be something really special.” With two brothers Conor and Daniel too, Mara admits she's less outgoing than Kate. “I'm so slow to warm, and my sister's very warm and open. She's lovely and people really love her. I'm an acquired taste.”

If there's that Salander-like reserve and detachment rearing its head again, it's certainly paid off in her work. On Dragon Tattoo, she utterly disappeared into the character – from watching Gaspar Noé's rape-revenge drama Irreversible to learning kick-boxing and talking to counsellors. Just don't ask her to explain her acting process. “I don't have 'a way'. I don't have a methodology, a set way of doing things. I come in and give myself over to the director, and try to do things their way.”

Just occasionally Mara opens up, lighting up those blue-green eyes. Like when I ask what the last film she saw at the cinema was. “The Croods!” she giggles, referring to the recent prehistoric cartoon. “I like animated movies.” But she can just as easily shut down; as when I broach the topic of passion versus responsibility – a big theme of Ain't Them Bodies Saints. Has she ever dealt with that? “I'm sure that I have. I can't think of anything specific, and even if I could, I definitely wouldn't share it.”

There's almost a wilful determination in Mara to withhold personal revelations – a trait both admirable and exasperating. In her eyes, because you act doesn't mean you need to offer up your life for public consumption. “Acting shouldn't be exposing. You're putting on all these costumes and putting on all these characters… I think sometimes acting can be a way for people to escape themselves and to be able to pretend to be someone else, and that shouldn't be exposing at all.”

The big question on everybody's lips is whether she will return as Lisbeth Salander in the sequel, The Girl Who Played with Fire? “I ask that same question a lot – I really don't know,” she says. Sony, who backed the first film, recently hired Andrew Kevin Walker, who wrote Se7en, to take a bash at the script – which is hopeful. “I'm ready for it,” says Mara – and she means it.

'Ain't Them Bodies Saints' is out now