YOU are her mama/mommy.
Your mother is her grandma, nana, or gramma, etc and so is your husband's mother. That you want your mother to have the name that is yours, but not his mother, isn't very nice.
I've been a daughter-in-law and am a mother-in-law. As both I was/am respectful of family member's boundaries. I am sure your MIL is aware of the fact that you don't like her, but you can't expect her to give up her son and grandchildren because of that. Without hearing all the stories, drama and hard feelings involved in the family history...can I just say; Please try to let things go and be more understanding so everyone can get along?
Why you don't just choose a grandmother name for each grandma, tell the grandmas that this is what your child will call them at this time and teach your child to use that name.