as far as your girlfriend goes, you need to be authentic with her. maybe she’ll feel differently when actually confronted with reality and not just a hypothetical. and if she feels as she says, you’re better off not wasting both of your time. you cannot stay closeted forever and eventually you two will have to confront this
I’d say you def need to let her know what’s going on because you deserve to be happy as well. Rn this is almost like a “fake” relationship bc you aren’t being 100%. If she stays that’s amazing and if she leaves at least you both then can find the true love you deserve. You deserve to be happy in your skin as well as with your partner!
i’ve been on the other end of this, in that i suspected that my boyfriend was trans and i am heterosexual. he ended up deciding he was wasn’t trans but the idea of him rejecting who is just to be with me makes me very sad. and im sure your gf will feel the same way. plus if you can’t be yourself around your partner they’re not truly a good fit for you.