You think she'll be mad?

Maybe. I don't know if that was the right kind of reaction, though. You were just as rude as she was with that response, so maybe you should look up those words as well. Tell her that you didn't do it, and you don't know who did, but since none of you seem to know who it was, all of you should work together to clean the bathroom. If she doesn't like that, then don't worry and don't clean.