The music world's feverishly preparing for this weekend's Grammy Awards. Some artists, however, need a little more preparation than others. JJ's Dirt passes along word that Cher - who will be performing a duet with Nelly Furtado - absolutely "bombed" during rehearsal. And, as if that's not enough, the legendary entertainer has been butting heads with the considerably younger Furtado:

Cher is acting like a HUGE diva and my source says, "Cher was being bitchy because the production kept being stopped and she was asked to work on certain things in her performance. Just things as simple as to where she needed to stand. Nelly's part was amazing and Cher literally bombed."

Finally Nelly said, "I need a drink!"

My source continues, "Cher's face is so 'red' right now. She is furious speaking to staffers her saying that Nelly had the performance all worked out her way and she didn't need to listen to a 'fucking kid!'"

She's kind of got a point there…