I've never gotten along with my s.o's mother. She's such a rude andunbearable woman. She thinks my fiance needs to still take care of her despite him having a family of his own already. She doesn't like me because I don't allow him to let her take advantage of him anymore. Anyways. About a year ago I invited her to our son's birthday party and she was so incredibly rude to everyone there. She had such a negative additude the whole time, took up all the time with my son so no one was able to be with him and whenever someone went up to say hello, she blew them off. I told my fiance she's no longer invited to anything anymore. Only thing is I'm planning a wedding and ofcourse he wants her there. I don't. I don't want her ruining my day with her bad additude and I'm actually considering cancelling a wedding all together, just to avoid having to invite her. Would it be wrong to not invite his mother or am I right to stand my ground?

Edit: she also has a drunk boyfriend who acts like an idiot when he drinks, he will definitely not be invited. I also forgot to add my mother and grandmother along with other family members can't stand this woman. My mother's already told me to sit her as far away from her as possible.