Joan Jett has nothing but high praise for Kristen Stewart’s depiction of the rocker in “The Runaways.”

“[Kristen] makes me very proud, because she’s a very real person, she’s really authentic, she’s dedicated,” Jett told Hitfix during a roundtable for the movie at the Sundance Film Festival. “She took it really seriously. It wasn’t a gig for her: ‘I’m doing this movie, I‘ve got something else down the road.’ She cut off her hair. She immersed herself, not only in the music, but in the story.”

Jett went so far as to give Stewart a tape of Jett talking when she was 14 so Stewart could nail her mid-Atlantic accent. Ultimately, the two women, who are now fast friends, realized they had plenty of similarities. “Just in real life, we’re a lot alike,” Jett said. “If you were to see the two of us sitting around, just the way we move in space is pretty much a lot alike, we shake our legs, put our hands…it was very similar.”

Jett, who serves as an executive producer on the film, had nothing to do with the casting of Stewart or Dakota Fanning as band mate/lead singer Cherie Currie, but she made one very specific request. “All I said to them about the casting was it would be really great if you could get teenagers because I think it makes a difference, you know, between even playing, if you’re 21 or 22. I know it’s still young and it’s still close, but there’s a little bit of a difference, that teenage energy, that was my only suggestion.”

As far as the accuracy of the movie, which is a fairly dark portrayal of the Runaways’ very quick rise and fall, Jett says she realized early on “that this was not a biopic… It’s basically a parallel story line that uses a lot of the Runaways’ factual stuff, but you know, there are embellishments.”

Of the romance between Jett and Currie portrayed in the movie, Jett is characteristically coy, saying only, “I thought they did a great job…I’m not a kiss and teller.” Currie, however, told Hitfix in a separate interview that the romance was “overplayed.”

One area that the film captured realistically was the resentment the band faced from its male counterparts. Men object to women playing rock and roll because it’s threatening to see women in so overtly sexual a position, posits Jett: “Pop music sort of presents itself as, ‘Here I am and you can do what you want with me.’ Rock and roll says, ‘this is what I’m gonna do with you,’ and I think a lot of times people find that with girls threatening. A lot of times people would laugh at us and go, ‘Oh, that’s cute.’ When they realized we were serious, they’d get nasty.”

And by the way, the group that refuses to give the Runaways a sound check in the movie is Rush, Jett said.

Wistfully, Jett wishes Runaways drummer Sandy West, who died of cancer in 2006 and who gets short shrift in “The Runaways,” were here to see the movie “because she was the one who wanted the Runaways to get back together and do a reunion tour and all that stuff. She would have been so proud. The movie maybe would have taken a slightly different, more expanded, role if she were alive.”

Ultimately, Jett wants viewers to take a positive message away from the movie. “Sometimes life is grim and you can’t lie, but also, there is a message of the underdog can win,” she said. “Dreams should be sought. You shouldn’t not go for your dreams because you’re told not do because it’s not what a girl is supposed to do.”