Just one week after it debuted, 90210‘s ratings have tanked. According to U.S. Nielsen ratings, this week’s episode saw American viewer ratings fall to 3.3 million viewers — much lower than the 4.7-million that watched last week’s debut episode. The ratings drop-off was even worse in Canada, where the second broadcast of 90210 dropped down to 664,000 viewers from 1.3 million for the debut. Meanwhile, New York Post‘s Page Six says Canadian actress Shenae Grimes who stars on the show, has been taking Shannen Doherty’s place as the resident bitch. An unidentified source told the gossip page that Grimes is “tormenting everyone on set,” and “acts rude to the cast, crew and extras.” She apparently even shouted “Who the hell are you?” at a guest star.