Leighton Meester is moving to Los Angeles now that her series “Gossip Girl” has finished. Michelle Trachtenberg hosted a dinner for Meester, plus friends and co-stars, at Midtown brasserie Lexington Brass on Saturday, to bid her bon voyage. After dinner, the group attended a “Gossip Girl” wrap party at the New York Palace. Later Meester and Trachtenberg, with Chace Crawford, Ed Westwick, Penn Badgley and Kelly Rutherford, continued celebrating at Meapacking District club Tenjune.