Fighting over baby names with my sister

Long story short my mother died in 2007 unexpectedly. My sister has always been overly vocal about using the name of she has a daughter. I have never said I wouldn’t use the name I’m just not the type of person who has always thought about baby names her whole life. With my first pregnancy we didn’t consider Audrey (moms name) as a potential name. With this pregnancy, as it is probably my last, I am considering the name should it be a girl. We find out gender next week and my sister asked my top two name choices. I told her I’m leaning towards using Audrey. She told me she has claimed that name already and I can’t use it. I don’t think she has any right to claim the name of my mother? She’s no where near the age or point in her life of having children. I think she’s out of line to tell me that I can’t use the name. If she was pregnant and claimed the name, or if she had claimed any other name, I would respect it. But A) she’s not pregnant and B) my mom was just as important to me and she was to my sister. I feel I should be able to honor her.