My coworker keeps using the “r word”

Hi. My (27f) coworker (35f) keeps using the r word at work. We work in the OR at a hospital. have told her multiple times now that I don’t like it when people say that word. Important info; i have a brother in a wheelchair. He is not mentally disabled.

Today, we were talking about Trump and she called him that word. I don’t care about politics so this is not about that. I asked her not to say that word and she said that she doesn’t mean anything personal about it or “anything against my brother”. I told her that my brother is not mentally disabled because he is in a wheelchair and that i have told her that multiple times and i don’t appreciate that word. She said that she’s going to keep using it and I can’t stop her from using it. I told her that we are in a professional setting, that it is not appropriate, and that a patient could hear her. She said no one is around to hear her and i told her that I was and i didn’t appreciate it.

I understand that to some people that it is not a big deal, but I have a learning disability and there are people at my work with kids with Down syndrome. Am I overreacting?