I don't want my stepmother at my wedding - what should I do?

You should speak to your father and let him know how you feel. He may understand a bit better when you tell him the truth. There is a chance that either way he will be upset, but at least he will know why you don't want her there. Is it possible that he knows she is outspoken and not happy about it either, but possibly willing to talk to her to tell her to be respectful to you? It is a risk you take, he may decide he will not come to your wedding without her. So is it worth it or not? Can you ignore her? Eventually someone will say something to her if they have not already.