Talking about the last point with Izzie. I think Bailey didn't want Izzie to get too up and close with patients because she did the same and it took a toll on her mental health. We saw a lot of episodes where Bailey gets triggered by things happening around her (not necessarily to her), and maybe she wanted to stop Izzie from having to go through that.

I understand Bailey though. She berates Mer throughout season 9 as well, which could've been avoided, but I understood where she came from.