Certain cast members of “Gossip Girl” behaved exactly like the obnoxious, ill-tempered rich kids they play on TV at Philippe Tuesday night, according to a fellow diner. Leighton Meester, Ed Westwick and a posse of their pampered pals barreled into the trendy East 60th Street eatery, cursing and talking so loudly that other customers complained, a source told The Post’s Jennifer Fermino. When one man at a table of lawyers and investment bankers politely asked Meester to watch her language, she allegedly shouted, “f – – – you! How dare you tell us to keep it down?” The spy added, “Other girls in their party were being really nasty, too.” Finally, Westwick jumped in and pleaded for peace, saying, “Don’t worry about my friends,” and, “We should all be happy. Let’s hug it up, guys.” Our witness ended up hugging affable Westwick. Reps for the actors didn’t get back to us and Philippe staff declined to comment.