P!nk and Christina Aguilera’s legendary beef boiled over during the making of “Lady Marmalade,” but there’s even more juicy backstory than fans realize. On Watch What Happens Live, P!nk described a run-in with Christina (presumably in the early 2000s) that turned physical. “You have to learn — women have to learn how to support each other,” she said. “It’s not taught to each other on the playground. Actually, she swung at me in a club. Hilarious! I was like, ‘What’s happening right now?