Can't a trans girl be gay?
Can't a cis man be gay, straight, or bi?
Why would being a trans man/woman preclude having interest in either sex/whatever gender?
Is it possible that your friend was extrapolating her own, personal preference, onto every other trans girl? Or are you doing that?
I don't see how is that better than portraying a character that is *NOT* like her.
Like, you know, a straight male gamer seeing the gay male character. The outrage, someone not like him.