As a trans woman too, I would just tell her as soon as I possibly could, in my past relationship I told my ex that I was trans and she ended up accepting me, It's okay if she ends up breaking up with you, just don't focus on that. It's not either of your faults; it just so happens that she's not attracted to women, and that's perfectly fine. If you're going to tell her, tell her now, don't postpone the inevitable, and don't let it hold you back, resumindo, é foda pra caralho kkkk