My mom's mother has an extensive history of ruining events by drawing negative attention to herself and speaking rudely of everyone around her (even the hosts!). She and my mother have had an extremely hit-or-miss relationship for the duration of my mom's life. She and my mom recently had a terrible spat and are not currently on speaking terms, though my grandmother has offered a lukewarm apology. I do not have a real relationship with my grandmother. She hasn't even acknowledged me in over a year.
Am I obligated to invite her? My mom thinks we'll look like the "bad guys" if I don't, but due to her history of taking any happy event and ruining it, in addition to the constant strife she causes my family, I do not wish to invite her. I need advice soon; our invites go out in a week!