Is this fair?!

I'm pregnant, and I've been discussing with my mother who I want at the hospital because she keeps asking. All I want there is my immediate family and my S/O and his father (the rest of his family won't be able to make it) and my best friend. However, I do NOT want her new husband there. She cheated on my dad with him, which lead to their divorce. And he has literally always made me feel super uncomfortable. I just don't get a good vibe from him, nor do I have a relationship with him. However my mom is basically throwing a temper tantrum saying I'm being selfish and immature and that he is "basically the grandfather" which isn't true because I love my father very much and her husband will NEVER be my child's grandfather. I just want this to be a relaxing day for me and I don't want people who I barely know there. I don't know what to do...