Kristen Stewart: Stepping out of the twilight

No wonder Kristen Stewart relates so well to her latest film, Snow White and the Huntsman. The fairytale heroine is on the run, pursued for her life; this actress knows what it is to be hunted too.

Outwardly, the 22-year-old's life reads like a fairy tale itself – Hollywood's top-earning actress of 2010; the girlfriend of Robert Pattinson, one half of celebrity power duo K-Stew and R-Patz – but her poisoned apple comes in the form of the tabloids with allegations that she's "miserable" and stylists find her "difficult to work with".

Quite the contrary. Close up, up the only hardness is in her choice of outfit: rock-chick leather trousers. She's polite, even awkwardly friendly, to the strangers around her. Stewart's gone from London for the world premiere of Snow White and the Huntsman to the Cannes Film Festival, for the launch of On The Road, an adaptation of the Jack Kerouac book by Walter Salles, who directed The Motorcycle Diaries.

"I am so self-aware, so self-conscious," she says. " There are people in life who lead the way and run after things, and then there are the observers and followers. I am one of those people; I'd be latching onto the leader. That's why I love to play characters that are so completely different to myself."

In Snow White, Stewart says she loves the fact "you have a kick-ass heroine, someone who can fight, yet she's not a strange girl pretending to be a boy. I always wanted to do something physically challenging and this was it."

Born in Los Angeles to a mother and father working in the industry, her first Hollywood role was as Jodie Foster's young daughter in 2002's Panic Room. She went on to do different bit parts before taking a turn in Sean Penn's critically acclaimed Into the Wild in 2007. This got her noticed; her subsequent casting as Bella Swan in The Twilight Saga and real-life romance with co-star Robert Pattinson has hurled both of them into the superstar league. She and Pattinson both have films competing at Cannes: the noise their "Twi-hard" fans made during their appearances made Brad Pitt's earlier premiere seem like a poorly attended funeral.

However, Stewart rarely allows herself the luxury of relaxing about her three-year relationship with Pattinson. At Cannes they went to each other's premieres, but didn't pose for pictures together. "That's private, that's mine," is all she's ever publicly said about her loathing of questions about her relationships.

The final instalment of Twilight is out in November, but she filmed those scenes a while ago. Apart from a previous turn as Joan Jett in The Runaways, this has been the year when she has finally been able to take on different roles: the armour-clad warrior Snow White, and the free-spirited Marylou, the heroine of On the Road. Stewart's name is much in demand; two years ago it was reported she had earned up to $30m.

"I always say follow the heart and things usually wind up where you want to be." Her attitude to what she wants is perhaps best summed up when she is asked about her On the Road character, Marylou, who Stewart says is a heroine of hers; it was a favourite book of hers as a teenager. " I love her spirit," she enthuses. "She's so genuine, so herself. She refuses to be a commodity and I love that."

And she can be downright naughty: she affectionately called her Snow White co-star Charlize Theron a "nutbag" when asked her opinion; her other co-star, Chris Hemsworth, who has played superhero Thor, says Stewart accidentally punched him in the face during their fight scenes.

It's those sides of Stewart that often go unreported; perhaps as she grows older, if she relaxes into her status, they will emerge naturally. Perhaps, with the end of Twilight, the fan frenzy will eventually cool enough to leave her to the private life she so desires, to do more of the things you'd expect of a 22-year-old.

Snow White and the Huntsman' is out now