Mother (Monster ) in Laws

My boyfriends (also the father of my son) mother has been stirring up drama since I've met her. She wanted/ still wants him to be with his ex whom was like her best friend. He's made it apparent that he no longer wants anything to do with her. This has been an on going 2 and a half year battle. He and I took a break while I was pregnant, while on that break she would text me saying how she just wishes we would get back together all the while texting his ex saying the same to her, planning lunch dates and things. The day we found out the sex of my son she kicks him out of the house after posting on facebook that she doesnt like me. The last time I had talked to her before that was a week ago and she was just so ecstatic about helping me as much as she could when the baby arrived. She goes through these emotionals ups and downs, has dragged my name through the gutter and I'm just sick of it. They went a few months with out speaking and now she wants to see my child and I'm not having it. Am I wrong? She tried to have me attacked while I was pregnant and also was the main source of stress during my pregnancy.