I wouldn't be able to stay in that relation. First of all it's something that should be shared before you enter a relationship together, by not sharing this information a transgendered person puts her/his loved one through a lot. I would feel my trust violated.
Second reason is more personal. I am a straight man and I find gay sex quite repulsive, we couldn't ever be intimate together. No matter what people say sex
is important to a long lasting relationship. There would also be the issue of children, I find the prospect of making children, these little humans that grow and share our genes incredably fascinating. It is something a couple shares, something that binds them together, not having that would be disapointing on itself.
Without that (slight) possibility of a long lasting relationship I wouldn't want to attempt it, no matter how much I like her or feel connected to her.
If it was a friend I would probably be a bit shocked, but wouldn't have any problems with it. The person remains the same, not like I had anything to do with her/his genitals anyway.
Sporky111 said:
T's not like they were lying to you, it's like someone who's gay/bi who never came out. It's not that they're lying to you, but that you made an assumption.
If it's your girlfriend... Technically it isn't lying but she
knew you would make the assumption she's female, she also
knew this would be a very large factor in wether or not most men would go into a relationship with her. Not mentioning it is akin to lying.