I have an upcoming wedding and I'm going to uninvite my mother-in-law.
Do you have a reason for revoking your invitation?
I don't want her there because I don't like her.
I can see why you'd want to uninvite her. But it's rude to take back an invitation you've already made, especially to a close family member. It will impact the relationship badly for a long time.
I don't fucking care, I'll make some excuse at the door.
Taking back the invitation isn't socially acceptable and it's even worse when it's done at the door. Your plans will cause a lot of chaos and unrest within your family and it has the potential to truly ruin your wedding day. I think you should just let your mother-in-law attend and try to keep your distance.