Who's the blonde socialite hooking up with TV's heir-heads?

"Gossip Girl" returned to TV last night with a mini-scandal for Jenny (TAYLOR MOMSEN) and even more humble pie for the dethroned "Queen B" (LEIGHTON MEESTER)! Now, Page Six reports that real-life heiress LYDIA HEARST will be joining the Upper East Side headband club for the show's cliff-hanging season finale.

In real life, Lydia (second pic) is one of the heirs to the WILLIAM RANDOLPH HEARST magazine and newspaper publishing empire. Now blonde, she was recently seen stomping the catwalks as a red-head at New York's Fashion Week. 

Also guest-starring next Monday on "GG" is former "Buffy the Vampire Slayer" babe MICHELLE TRACHTENBERG as Georgina Sparks, a girl from Serena's past who threatens to take her down. And a new hunk (Broadway's JESSE SWENSON) catches Jenny's eye!