ALERT LC!!!!! Kristin and Nick are OVER - time to swoop in for the sloopy seconds for the 100th time!

There will be no kissing under the mistletoe for Kristin Cavallari and Nick Zano this Christmas. "They broke up," a friend of Kristin's reveals exclusively to Life & Style. "She moved out of their house. They're going in separate directions." Kristin, 20, just moved in with Nick, 29, this summer. So what happened? "It wasn’t working out," explains the friend. "She was bored, and I think she realized she was better off keeping her options open." In other words, Kristin missed the single life. "She used to be the It girl, and now she sees all of these other girls who would normally be in her shadow stealing the spotlight," says the friend. "I think she wants back in on the scene. So get ready, Hollywood — here comes Kristin Cavallari again! Living together put a real damper on things," says a friend.