He told me, and plenty of other people
Your missing my point here. He told everyone else, he didnt tell her until he knew for sure that she liked him. That changes everything. Had you told her early on then it would of been okay, but when you get her to like you and then you say "I like men to" it makes a difference. It probably didnt help that you said "I wouldnt ever cheat on you". She probably thinks that you already have.
Dont feel bad. I hope I didnt hurt your feelings or anything. Its just the way that you describe the situation makes it look like your the bad guy. Your not a bad guy, what you did in the way that I see it though was wrong.