Am i overreacting?

Okay so i was with my MIL yesterday and she randomly brought up the fact that when the baby is born she is going to be called mama. I told her no and that i didnt like it because the baby would be calling me mama, mom, mommy etc. And that i didnt want to confuse him when hes older. She got snarky with me and told me she didnt care and she was gonna be called mama anyways. I just think its too close to mom and i think its disrespectful of her not that care that i dont want her called that. I just feel like thats not a name for a grandma. Would you be mad or am i overreacting?