She's a queer girl, a femdom, a lesbian. But she made an exception for you, so she said.
It was nice having a girlfriend... a very normal desire for a very *cough* normal guy like you. It validated your ego to be in a straight relationship. After all, it is more difficult to find a partner with your, ah, predicament.
The sex is fine (although she sometimes focuses too much on your chest and your boyhole for your liking. Relax, nobody's perfect) but she says she likes pretty boys, femboys. So, reluctantly, you let her dress you up in thigh highs and mini skirts and makeup.
It feels uncomfortable but somehow exciting. She persists: long wigs, collars, slutty lingerie. She still calls you her pretty boy, her good boy, but when you look at yourselves in the mirror, it looks like two lesbians having sex. You feel dysphoric, sure. But you feel longing, lust.
You keep chasing the feeling of bliss, you dress more feminine in public, you become lazy with your T shots (much to your girlfriend's delight and support). You suddenly don't mind when people acknowledge what you have as a lesbian relationship. Your girlfriend says you are both proud lesbians, you nod dazily. You not only begrudgingly let your girlfriend grope your tits and soaking pussy, you encourage it. It's never felt to good. It feels so good to just give in.
Eventually, you can't even cum unless she's calling you a good girl.
Because this, my "straight" fakeboys, is where you belong. As a good girl, and toy for a lesbian. Submit.