Stewart has hung out with Jett to perfect her transformation

‘Twilight’ actress Kristen Stewart has been spending time with rock icon Joan Jett since being cast as her in ‘The Runaways’, a film about the 1970s all-girl rock band of the same name.

Originally meeting before Christmas last year, before Stewart was cast, the pair spent June 15 together at Sunset Sound Studio in Los Angeles working on Stewart‘s guitar and vocal technique.

Stewart has also had her hair into the classic jet black mullet which Jett sported in the ’70s, reports the Daily Mail.

“She sounded great and played well (on the guitar). She has the passion for it, which you can’t really be taught,” Jett said.

“I’m just listening to her music all the time. I’m trying to just make myself aware of the time period and what she was going through,” said Stewart. “It’s one of the most immense responsibilities to play a real person. Her story’s important. It’s an incredibly triumphant feminist story really.”

Dakota Fanning is also to star in the movie, playing Cherie Currie, the band’s frontwoman.

The Runaways will be the first feature film from Floria Sigismondi, who has directed music videos for The White Stripes, Interpol and Muse.