Ok I'm a gonna shout this in big letters.
NEVER TALK always DOCUMENT.
Your teacher is transphobic and she's full of shi! Document a letter to the guidance counselor, teacher and principal and state that you would like to be addressed by the other name.
She's lying. Kids have all sorts of different names and as teachers you address them by the name they tell you. I teach Chinese Kids every weekend and half their names are like Pey Ying, Mei, Xiaou etc and they go by Rachel, Mary and Jimmy. She's being discriminating and you must document it.
Document it.
You don't have to be mean about it. Just dash off a note that says, wait just copy this:
Dear Ms. Teacher, Guidance Counselor and Principal,
I am writing to formally ask to be addressed by a different name in the classroom. Although Ms Teacher knows I prefer to be called Fabulous she has told me that it is her right to call me by given name. Is this true? If not I'd like to be referred to as X.
I would like to have someone explain to me the procedure for changing my name in the classroom.
Thanks so much for your time and consideration.
DATE IT. MAKE SURE YOU DATE IT AND SIGN IT
stupid teacher.