MIL controlling what we name our baby

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So my husband and I currently like with his parents while we shop for a house. I’m also pregnant with our first baby. My MIL will be the one watching our baby while I’m at work 2 days a week due to ya not having any other family In the area. She’s a great mom and I know she’d be a great grandmother, but here’s the problem: She’s the type of person that always has to be right and if it’s not done her way she gets an attitude and proceeds to do things her way anyway. my husband and I have the names picked out, names which we both love and are special to us. My MIL can’t stand the names and gets so upset when we tell her we’re dead set on them. Last night she told me that she was going to find nicknames for the kids and call them that because “ I’m not calling them by that name it’s stupid and I hate it” I don’t care if she has her own nickname for the baby, but she processed to say that’s how she’ll introduce them to everyone.... I want my child to go by their name, not some nickname... and it really upset that she did that. Am I being over dramatic or is she wrong? What advice do y’all have for me? We’re hoping to be in our first own house before the baby is 6 months old and every time we talk to her she gets defensive and upset and won’t talk to anyone for days, then proceeds to do things her way anyway