"You only have one life," Kate told ET. "I don't want to spend my life worrying about how I look or what other people think."
In the film, Kate plays Erudite faction leader Jeanine, who is hunting Divergents in the hopes of finding one who can unlock a mysterious box. The rebel group rallies around Tris (Shailene Woodley) when it becomes clear she's the one Jeanine is after, in order to prevent her capture.
"People have been saying, 'Gosh, you're not known for doing these big franchise pieces and playing the baddie,' and it's like, 'Isn't that great!'" Kate told ET.
Miles Teller also stars in the second installment in the Divergent series and he showed off his new ripped body on The Tonight Show Starring Jimmy Fallon. The actor brought along before and after shirtless pics of himself that revealed his progress in the gym.
The 28-year-old bulked up for the role of World Champion boxer Vinny Pazienza in Bleed for This.
Insurgent is in theaters March 20.