There's a new Dawn over at the CW.  

A rep for the network confirms that Michelle Trachtenberg has joined the cast of the privileged-teen-centered soap Gossip Girl, in which she'll play one of the bitchier members of the bunch. 

On the freshman CW series, which has been renewed for 2008-2009, she'll portray Georgina Sparks, a mischievous minx from Serena's past who will inevitably stir up trouble for the recently repatriated Upper East Sider, per TVGuide.com. 

While as Buffy Summers' sister Dawn on Buffy the Vampire Slayer, Trachtenberg was the mythical "key" to an exiled Hell-God's plan to return to her evil domain and lay waste to the town of Sunnydale.

After Sunnydale went "poof" in 2003, the 22-year-old Trachtenberg, herself a New York native, went on to starring roles in films such as Disney'sIce Princess, the teen-hustler drama Mysterious Skin, the Yuletide slasher flick Black Christmas and the made-for-TV tearjerker The Dive from Clausen's Pier.

She has also had prominent guest spots on Six Feet Under, House and, most recently, Law & Order: Criminal Intent, the show all actors seem to go to for help exploring their sociopathic sides.