I'm not trans.
I hate my legal name. I will change it when I'm ready to do the paperwork. Until then, everyone calls me the name I prefer.
I would have been a thorn in this teacher's side. I'm not answering to that name, asshole. I'm not writing it on any documents. I'm allowed to tell you what to call me for whatever reason I want. My mother's best friend, who I was named for, was an abusive fucking cunt to me and every time you say her name I'm reminded of her.
What a douche. Stop policing names. The only names worth policing are the ones that are remarkably dumb.
And to add my own experience; if you have family you despise, don't worry. They'll outlive the heat death of the universe.