Boyfriends mother issues!!

So I've never met my boyfriends mother because she has flat out refused to meet me. She told him I'm no good for him and he needs to go back to his ex because I'm a slut and dirty. Keep in mind this woman has never so much as laid eyes on me, let alone knows me. So he has a 4 yr old daughter with this ex and she is all about her granddaughter which is awesome, she should be. We told everyone in August that we were expecting and her words to him were.. "I only have 1 grandchild." It hurts him everyday but he said if she feels that way so be it. I feel bad but I've stood and made my grounds that she is allowed no where near our son, Kyron. I feel guilty for my choice but she has said horrible things and can't act like an adult and be happy for her son. His ex is having a baby and she's even gone to the extent of calling thag baby her grandchild. And no, they were never married. Has anyone been through this? Advice? Encouragement? Anything? Sorry it's so long