Gossip Girl (2007): Season 2, Episode 4

2 - 4: The Ex-Files

Blair and her minions decide to befriend the new girl Amanda (guest star Laura-Leigh) in order to sabotage her. Vanessa discovers a scandalous secret about Catherine and enlists Blair's scheming expertise to use the information to help Nate. Meanwhile, Lily finds herself drawn back to her ex, Rufus, once again.