Abbie Cornish is preoccupied with her tan. It’s a notably superficial concern for an actress who seems completely without vanity. In 2006’s Candy, she played a heroin addict with red-rimmed eyes and matted hair, and in her current film, Stop-Loss, she fought to forgo makeup altogether.

“It was a negotiation,” she says. “It was me saying ‘I don’t want to wear any.’ And them saying ‘Wear some.’ And me saying ‘Can I just wear a little bit?’”

Now the 25-year-old actress has a month to get pale. She’s set to begin filming Jane Campion’s new movie, Bright Star, in which she plays the poet John Keats’ lover. By then, her complexion—currently tawny from three months spent at her mom’s house on the coast of her native Australia—will have to be back to its usual Vermeer-grade porcelain. “I was putting on sunscreen every two hours,” Cornish says. “My family was laughing at me because I had my hat on.”

Maybe it’s that she’s fresh from the beach. Or it could be the homage-to-bohemia outfit: white lace top, military-style jacket, red rubber Wellies, and thumb ring. But at a diner in the Los Angeles neighborhood of Los Feliz, as Cornish slouches against a wall and twists her wavy blond hair into a ponytail, she looks more like a lovely, disheveled wanderer (the kind every guy hopes to meet on his soul-searching trip to Europe) than a movie star who got a standing ovation at Cannes in 2004 for her first leading role.

After seeing Cornish in that role in Somersault, as a teenage girl who runs away after being caught in bed with her mother’s boyfriend, Stop-Loss director Kimberly Peirce cast her as a Texas girl who takes off with the best friend of her soldier fiancé, played by Ryan Phillippe.

“She’s phenomenal,” says Peirce, whose last movie was Boys Don’t Cry. “She just holds the screen.”

Since Cannes, Cornish has gotten acclaim for her acting, but, to her frustration, American audiences still know her better as the supposed catalyst for Phillippe’s divorce from Reese Witherspoon. Both Cornish and Phillippe have denied a romance but say they’re close friends.

Paparazzi generally leave the actress alone when she’s solo, but not when she’s with Phillippe’s children. When she’s asked if it’s hard for her to be photographed with them, Cornish’s eyes begin to water and she presses herself closer to the wall. “It’s difficult, because you’re just taking a kid into a store,” she says. “The bottom line is that you’re just living.”

Cornish has been nomadic for the past decade—at 16 she moved from her parents’ home to an artist’s loft in Newcastle (a city north of Sydney) —and prefers Australia to California. In Australia she performs what she calls “underground Aussie hip-hop” in a group made up of her (she raps) and two guys. They recorded their third album last year. “The studio was in my house,” she says. “I’d get woken up by the boys at the door with their skateboards, being, like, ‘Come on.’”