Credit: Courtesy of Seventeen

Twilight was fun while it lasted, but Nikki Reed is ready to move on.

In the December/January issue of Seventeen (on newsstands November 22), the 23-year-old newlywed admits that "in the beginning, it was innocent and fun, and we were like one big happy family. It was like being at sleepaway camp."

That all changed when the first movie premiered in 2008. "Success came along and changed the dynamic," Reed says. "We're not all best friends, and we're not all going to hang out together after the final movie is done."

Reed, who plays vampire Rosalie Hale in the series, admits it was difficult to see her costars' relationships deteriorate when cameras stopped rolling.

"It was very, very sad. Let's just leave it at that," the actress -- who wed former American Idol contestant Paul McDonald in October -- tells Seventeen. "Attachments grow when you're working with the same people for so long. People are friends, people fall in love, people get in fights. We're not all robots in that way. Sure, things have gone on, and it's weird to have them be in the public eye."