It rarely is seen to include drag queens and tomboys. Some might use the term queer, which isn't really an insulting term but often has been as wider umbrella term, including homosexuality too. And transexual also means someone who has or is transitioning.
I think that rather than coming from too much idealism, it'd be beneficial to inform yourself on how people talk about these things in the communities, so that you can avoid even further losses of friends that are in those realms. You do come off as being at least slightly insensitive, so it's normal that sensitive people will have trouble with that.
That said, I think anyone can say whatever they want. It's just.. sometimes certain things can hurt people.
You dont deserve to be hurt either. It's just complicated when someone is triggered by things said. Maybe with time there'll be opportunities to talk with her again. If they're sensitive tho maybe they need more time for themselves or in their bubble.