My mom picked an awful grandma name

My husband and I are having our first child and have only told a few people since it's still early, I'm almost 10 weeks. My mother is one of the people we have told and she has already picked her grandma name. It's Kitty. Not grandma kitty, just Kitty. I absolutely hate it. She's one of those people that is very anti-aging, she had like five 29 again birthdays when I was a kid (she had me young) and I just think Kitty is a ridiculous name to give yourself. I told her I didn't like it and she said we'll it's not your choice. Am I overreacting to this? I've told her that I will not be referring to her as kitty to my child. She's not ever going to have access tomy kid unsupervised anyways, so I don't really see it sticking.