I'm conflicted with the dance mistake. Mei did the dance exactly as practiced, so it was Karin who made the mistake but it will look like it's Mei's fault. But on the other hand, like Mei realizes, it only happened because she didn't care about anyone but herself. So Karin is at fault but Mei will probably get dinged still for not being able to adapt and having to be saved. Although a part of me thinks it would also be smart (yet evil) if that was all a calculated move by Karin to ensure she wouldn't be eliminated. She'd be doing whatever she can to survive despite having Black Star teammates. But knowing the author I don't know if they'd ever make a character do something that scheming. Although this is a survival contest so you never know.
Either way, Mei's backstory makes me so sad man...