It all comes down to a matter of opinion really. Just be honest with her about it and suck it up kid. It's like this, you'll be a douche in some peoples minds, sure, but in your own mind you made the right choice, and since it's not meant to be hopefully people will realize you were just doing it for the best and possibly admire you for handling the situation well.
But there are totally douche bag ways of handling this shit too, so uh, your choice.