"I know this is going to sound bad but I'm really glad ['The Ugly Truth' is rated] 'R.' I didn't want to do another 'PG-13' movie," the actress told InStyle's August issue.
"You're probably going to drop the F-bomb once in a while. You're probably going to say some things that are kind of harsh," she said of being able to depcit a realistic relationship on-screen. "And you're definitely going to talk about sex. It doesn't have to be so Snow White and Prince Charming."
Besides adult-only content, Katherine explained that she wants to tackle hard-hitting topics in her upcoming work.
"Studios love stories about the man or woman who has had nothing happen to them other than their own bad choices," she said. "I'm much more passionate about the people who survive not the choices they've made but the s*** that comes down in life that you have no control over. People who lose children or suffer great illnesses or disease and yet manage to come out of those experiences still passionate about life and joyful and grateful to be alive. Those are the stories I really want to tell."
And when it comes to the story of her own Prince Charming, husband Josh Kelley, the 30-year-old actress said she got lucky after years trying to figure out love.
"In my early 20s, I didn't know who I was or what I wanted I was fed up with trying to be somebody else," she told the mag. "And [then I] got really lucky and met a great guy who loved me for me."
"The Ugly Truth" opens in theaters on July 24.