In the movie, Carano plays a covert ops specialist who's been double-crossed, so she's striking back with all her might.
The action-filled thriller from director Steven Soderbergh is set in the world of international espionage.
There is plenty of fighting and Carano - who has fought professionally - came prepared.
"My parents always taught me never back down and so I didn't. But I never went out looking for trouble. I'm not a bad girl. I'm just a girl that stood her ground," Carano said.
In "Haywire," she stands her ground with co-stars Channing Tatum, Ewan McGregor and Michael Fassbender.
Anyone who would do this role would need to have a certain physicality, which Carano clearly has. But as her first major role, choosing Carano was a risk.
"It was definitely a risk," she said. "I think that's what makes him so great, is you take big risks in life and the bigger ones you take, the more you learn from them."
Carano said she was comfortable with the fighting and the action, but her on-screen smooch was a little intimidating.
"Kissing Channing, I think he probably felt my heart beat through my mouth," she said. "He's like my brother, but at the same time, I've never been ordered to kiss someone in front of people and it's all quiet and the camera's right there and you're like, 'I hope that people consider me a decent kisser, because that's going to be on film forever.'"
"Haywire" is rated R for its violence. It opens Friday.