This whole thread is insane.
No, showing up at the Met Gala will do squat as musical promotion - it is a fashion event, not a music event. Only one person performs, and that is decided by Anna Wintour. So anyone claiming this would be massive musical promotion is smoking something.
Good for Rose is she is going, and honestly, it is stupid to care about who is or isn't going to this fundraiser, which is what this event is.
I don't care whether Lisa goes to the MET gala or not. But her promo schedule is bare at the moment, and that better change.