Am I being selfish?

My fiancé mother is a horrible woman! Because she doesn't like me or the fact I am having a child with her son and we are getting married she called the cops had him arrested on bs charges. Today she could have dropped them but instead she refused to sign the affidavit. She called me up asking how I was doing and blah blah blah. Unfortunately I have to be nice to her because he has another court date in a month. But as soon as this case is dropped I am giving her an ultrasound picture and explaining to her that is all she will see of her grandson. She will never know his name nor will she have any contact with him! I know people say don't keep children away from their parents and grandparents but she has caused me so much pain and it's all because her son "wasn't supposed to marry me" he has missed out on the past 15 weeks of my pregnancy by the time he gets out (if he gets out on his next court date) I will be ready to pop. I don't want to give her the chance to hurt my son, and right now she has never showed me any reason to believe she will change. 😞