first of all : you’re right, it is unfair of her not to listen to you! but maybe she has her reasons (like not feeling informed enough on the subject to help). i would try and ask her for her motives, and explain how it made you felt, and try to clear it up. if it turns out it really was for homophobic reasons, then you are allowed to get angry!
sometimes people dont like to label themselves as a lesbian because they have negative associations with the word. that’s the same for me. does calling yourself gay feel any better? the problem might be as simple as that
if not, it might obviously come from internalized biphobia/lesbophobia, where you don’t actually dare to call yourself something, but there might be other reasons
crushes on boys can come from coerced heterosexuality, where you force yourself to like boys, or interpret any positive feelings toward a boy as romantic attraction. does that sound familiar?
those are the first ideas that come to my mind, but of course im not all knowing, i can only provide my own insight. feel free to ask if you want to make some things clearer!
also, remind yourself that your labels are completely up to you, and if it doesn’t make you feel comfortable, you are under no obligations to anyone to use them
Fuck JKR 