Sneak Peek: Gossip Girl (The Ex-Files)

Check out the clips below from Gossip Girl (The Ex-Files). Blair shows you how Mean Girls really get down.

When Serena (Blake Lively) notices that Dan (Penn Badgley) has been cozying up to the new girl in school, Amanda (guest star Laura-Leigh), the ever-loyal Blair (Leighton Meester) and her minions decide to befriend Amanda and sabotage her budding new romance with "lonely boy."

The new episode of Gossip Girl (The Ex-Files) airs Monday @ 8/9 c on The CW.