This would be my reaction if it was my son. I'm not saying it is right or wrong but here goes.- I would not count on the principal. I think that it's good you had the conversation because I'm sure it informed her of something she would otherwise be oblivious to, but I'm not sure how much action she will take.
My coworker recently went through something similar when his daughter transitioned into a son. He was very supportive whereas his wife was very against the transition. Listening to his journey informed the opinions above. I guess sometimes I lean toward tough love and expletives, but I think that we can only do so much for our kids. Pick our battles, so to speak. Education and honesty are key. What do you guys think? Would your advice be different? I'd love to hear your feedback.
EDIT: This article.