Credit: Courtesy of Esquire

Minka Kelly may look like a nice girl, but back her into a corner and she'll show you who's boss.

In fact, the 30-year-old Friday Night Lights star admits she once picked a fight with a girl in high school.

"I'm a very nice girl, but nobody pushes me around," Kelly, named Esquire's Sexiest Woman Alive, tells the magazine.

In her school days, Kelly hung around with a girl who came from a family of kickboxers, and learned a few moves from her pal. When a fellow student pushed Kelly over the edge, Kelly ended up sparring with her in the school yard, Esquire reports.

Mess with her friends and "that's when you'll see a whole other side of me," Kelly says. "That's when you'll see the side that grew up in Albuquerque."

Now, the former scrub nurse turned actress, who turned 30 in June, is much more comfortable in her skin.

"I'm so excited to be a woman," Kelly -- who dates New York Yankees player Derek Jeter -- tells Esquire. "I'm confident in my skin, and I'm cool with my flaws and all that stuff."

So cool, in fact, that she stripped down for a series of sexy shots inside Esquire's November issue. See more steamy photos here.

"I think my thirtieth birthday gave me permission to have all that," the actress confirms. "The twenties were a pain in the ass -- figuring it all out." What will her 30s bring? "I don't know," she reasons. "And I'm glad I don't know."