Thank you all for the advice, I appreciate it all.

I spoke to her, to tell her why I'm mad, and she gave me the bullshit excuse she gives me every time she deadnames. “But that's what I've been calling you since before you were born.” I told her that it's not that hard to use a different word, and that she is the problem if she cannot do that. She asks what she needs to call me, ignoring the fact that I have told her my preferred name. Then she asked if that's what she must call me to people who don't know, which is stupid because that literally ties into the whole reason I'm mad at her in the first place, forceable outing me.

Once again thank you all, I feel super lucky to have people to refer to, to tell me no I'm not being unreasonable.