DO start documenting everything though. You want to build an unimpeachable dosier on this woman. If she's pulled this crap before, you can be she has made a lot of 'if not enemies' at least willing allies for your next move.
Do not under any circumstances drop out. Sets a bad example for your dd and also for this other little girl. You're tough. You can do this. Think of it this way ... it's fencing in real life. ;-)