Mariah Carey and Rihanna refused to talk or be photographed together at a Halloween bash. The dueling divas worked hard to upstage each other at Carey’s party at M2 Ultralounge. A source said Rihanna, dressed as a tiger with a tail so long a security guard had to hold it up, partied with three female friends and rapper Ne-Yo in a booth and wouldn’t cross the dance floor to pay her respects. Meanwhile Carey, in a corset and giant angel wings, stayed with hubby Nick Cannon in her VIP area. A spy said, “It was Mariah’s party, but Rihanna didn’t want to be seen with her. And Mariah was not going over to greet Rihanna. Mariah needed six guards to clear a path to the bathroom so her wings wouldn’t be dislodged.” Carey’s rep said, “There were 1,000 people there and, of course, she needed security. She heard a rumor that Rihanna was there but she never saw her. She loves Rihanna and of course would have said hello.” Rihanna’s rep had no comment.