Dear "New" Crush,
I'm completely unimpressed with your g/f, and actually somewhat insulted that you'd rather date her. I wish I had the courage to tell you that in person, but I don't. Just know that I'm judging you a little bit, and nursing my wounded pride.
Consider me having totally given up, because I'm not even sure I would want to date you now, especially if she were to break up with you because I do not want to be second best to her. I know this makes me sound completely egotistical, but you know me--I have less self-confidence than would fill a thimble. That said, losing to her makes me sick because I'm sure I have at least as much to offer as she does, and I suspect I have more.
Maybe some day I'll find someone who does want what I have to offer. Maybe not. But you made your choice, and I'm not impressed. And given how much I generally admire you and your decisions as a friend, that makes me sad.