Blair Waldorf? Serena van der Woodsen? Let's be real, the best Upper East Side mean girl was always Georgina Sparks on Gossip Girl.

Georgina was played by the actress Michelle Trachtenberg, who was found dead at 39 in her Manhattan apartment on Wednesday. Her performance as the teenage supervillain brought an arch flair to a character who was only a minor figure in the novels that were the basis for the show, but became a fan favorite onscreen.

The actress played socialite Georgina Sparks on the hit CW series Michelle Trachtenberg’s Gossip Girl costars, Ed Westwick and Chace Crawford, are paying tribute to her after her sudden death at age 39.