I had something like that happen but in the opposite.
Context: My girlfriend (lets call her Girl A) had broken up with me, and one of her friends (lets call her Girl B) started to take an interest in me. We would all hang out in a group. Myself, her, one of my close friends, her boyfriend, another one of my friends, his current girlfriend of that moment (Changed pretty frequently.), my Girl A, her new boyfriend, another one of my ex's, her boyfriend, (I didn't care about her. They day she broke up with me, I waited until I was out of sight and pretty much danced off smiling. I later found out she had told people that I was heartbroken...weird.)
So I did the natural thing and stayed away from my ex (Girl A) making out with her new guy, and hung with the people I could stand to see making out. Eventually, Girl B invited me over for a party. At the end, everyone had left, so She and I were alone together. She snuggled up to me and went for a kiss. That was one of the worst timed moments to suddenly figure out my romantic feelings. I turned to her and said, "I can't do this, I still love Girl A" and left. I turned down a Hot girl who was coming onto me in a empty house.
I apologized to Girl B many times for doing that to her. She understood, and was nice about it.
However, there was more. A couple months later, Girl A said this to Girl B, "I think I love Henry, (that is me), but he will never take me back, he must hate me now."
Girl B was completely over me since she said, "The Last I heard, he still likes you."
A few days later, Girl B told me this, through the power of 'HINTS!' via direct questions asked them by "a friend".
Thus began my current relationship.
(This was 2 years ago, still going strong.)