SO's mother (From hell)

Ma

So I've been with my SO for almost 4 years and his mom hates me. Partly because every time we argue he runs and tells her all this bad stuff about me and what I supposedly did to him. The other major part is he's a mamas boy and her youngest. She is a minister in the church but I swear she's the devil in disguise! I get a really bad vibe when I'm around her. That's my baby's grandmother and I don't feel comfortable around her not one bit. I stay away from her at all costs. If we do speak it's the basic hi how u doin? Good n you? Fine. That's it lol How can I deal with this situation better since this is my baby's grandmother? I don't even think she thinks the baby is my SO!! She never asks me anything about the baby or how my pregnancy is going. He says she asks him all the time I think he's lying tho.