I'd just like to get everyone's opinion about what they would do in this situation. Here's the setup:
My fiancee and I are getting married at the end of May, so we have already sent out of save the dates months ago. One of these was sent to my sister's mother-in-law because we see her at some holidays, and I thought my bro-in-law would appreciate it. My sister and her mother in law have never really gotten along because they are two very different people, we had never really saw/heard for ourselves why until recently.
About a month ago, we went on a family vacation to Disney World which included my sister, bro-in-law, two nieces, my mom, and sister's mother-law. Well, it went south very quickly because apparently there has been some jealously brewing on the side of my sister's mother in law towards my mom that we had not really realized because we hadn't spent THAT much time with her. Every time that my mom would want to hold my nieces hands or give them attention, we would get a very loud "UGH!" and an eye roll from mother in law. Every time my sister and bro-in-law were not around, the mother in law would actually insult and say very cruel things to my mom. Things like "my mom is just miserable because she doesn't have any friends" (which is not true, and how would mother in law even begin to know that) for example. This went on the entire time. She always had to make a big scene about everything and was completely childish, and my mom was completely done with her after the vacation.
First off, I'm completely disgusted by her behavior, and the fact that she acted that way towards anyone is completely unacceptable. Secondly, I would like everyone's opinion of what they would do in this situation. I know its completely rude to send someone a save the date and not send them an invite, but I literally cannot stand the thought of that woman being there at my wedding knowing that she acted that was to my family and knowing that there's a good chance she'll cause a scene again.