Our characters, in our storyline (that is to say, yours and mine) are basically the equivalent of married. They live together, are (were?) derpy in love, and so many other things that are fine, since you prefer the more sweet side of RP normally and try to avoid too much conflict. It's cute, and I am fond of it overall, so that's fine.
What you roleplay with your character outside of our storyline is fine with me and not really my business. I don't care how many AU's you have of him with other people - I've been known to do the same, especially with my elf - what can I say? He's popular. I just don't let them overlap, because it gets awkward. I've made that mistake before myself and luckily it was accepted and retconned and all was well.
You made it awkward. Really awkward.
You have a friend who is sweet and nice and wonderful OOC. I even like RPing with them! What I don't like is for you to suddenly decide that your new one true pairing is ...all three of our characters together. In character, even. To add a bit of salt to the wound, you created a new backstory where your char and theirs had met and fell in love before your character met mine. They were separated by faction boundaries (Because the other person is from the other side of the WoW fence) and war and other things that happen but apparently always carried a torch for one another. Bear in mind, when our characters met a year and a half ago, your character suffered from none of this melancholy you speak of now. At all.
But to say that your char, upon rediscovering their forbidden love, would go behind my character's back to be with them and expect my character to accept it, that, that is what angers me. You seem to refuse to accept that they have any right to being angry just because your character "has a heart big enough for two."
That's all well and good, but disliking my IC reaction when you let them know that the person they dared show just a bit of trust to, enough to fall in love with over a year+ of RL time, it hurts. It goes beyond hurt into annoyance when your character gets mad at mine for being angry!
My character is not going to take this betrayal well, and you are completely mystified as to this point, to my displeasure. He is a Blood Elf. They do not take betrayal well, and breaking it off cleanly would be the least of the things he could do. Normally, he's a rather likeable sort, but please be prepared to accept that he is not going to fall into a bed with you and your cross-faction lover just because you think it's hot. :|