It's a Gossip Girl Cat Fight!

Gossip Girl is back with new episodes, and while the show has turned up the heat with revelations that a character will come out of the closet, things are getting fiery behind the camera, with New York magazine revealing that onscreen frenemies Leighton Meester and Blake Lively "avoid each other like the plague," leaving their castmates to "choose sides."

An insider also tells OK! that Leighton "is jealous of everyone. She doesn't like her character's wardrobe. She thinks it's conservative and she's more fashionable and sexy in real life. She once said, 'I look like a dork in my outfits.'"

And with the spotlight on the show's other actors, Leighton is feeling left out. "She wants to be a movie star and wants the publicity that her co-stars are getting," says the insider. Leighton's rep denies the claim.

The source also confirms, "Penn Badgley and Blake are a couple and so cute. They hide it from cameras and go to dive bars and stay out of the limelight. They're low-key, but such a happy couple."