Mother stole my name!

So, for literally 7+ years I have loved the name Mia and my husband and I just knew we would name our first daughter Mia. It is significant to me because I have been a nanny for 12 years and cared for so many babies and finally I would have my own, Mia means "mine". So recently I realized my mother chose the grandma name "Mia" and already has my sisters daughter calling her "Mia" (instead of grandma). We brought it up to her and she acted shocked like she didn't know but never offered to change it. Ugh. Frustrating!!!