From today's Page Six:

Is there a beef between Madonna and Janet Jackson? Madge was chummy with fellow singer Shakira at Butter Monday night (our spy said they showed up "hand in hand") and was spotted dancing on banquettes with Demi Moore, Ashton Kutcher and Penelope Cruz. But Jackson was holed up a few booths down and, "She was not invited to join Madonna's crew," said an onlooker…

Two people in the same industry didn't hang out together so it should assumed that "beef" exists? If one accountant sees another accountant at a bar and doesn't invite him over is there "beef"? I think the only meat that was there was all that Kabbalah bologna.

There's more.

[Source, Source]