OMG. I can't even imagine that horrible culture! I grew up on swim teams and two of my three kids are swimmers and we've been so lucky never to have experienced it. I would bring it to the coach's attention again and ask that the coaches have a team meeting outlining the rules of behavior and consequences for poor behavior. I don't see how you can encourage your dd to be mean back, but I would certainly encourage her to hold her ground when she's right. Then, it's kind of up to your dd to determine how much she can take if the situation doesn't improve.
I know it is an effort to find a team with the right culture. We turned down one team that seemed too cut-throat. If I were you I would still be calling around to the different teams to see where you can find an opening, and asking if not now, when might they have room? I would also ask for recommends from the other coaches-- maybe they know a team that has an opening.
So sorry your dd is going through this. It's impressive she wants to put up with it in order to swim.
