Trans women are women. You didn’t even realise she was trans, and then you get mad when you find out? All humans were born as children, that doesn’t make you a pedophile, does it? Why does it matter what genitals she was born with?
But that’s beside the point. It doesn’t matter if you’re not fully comfortable with your labels yet. You don’t have to decide, nobody is pressuring you. Take your time, experiment, figure it out.
Also, you would be aromantic, not asexual.