IMHO - It's already too late.
She's already probably banged the dude - so do you want her REALLY back? Personally I wouldn't touch her. Sure, you're probably thinking "well everyone has had past lovers before "you" come along", and that's probably true, but you don't want to be the dude that picked up and ex after she went out and got some strange - it's a different situation, and not a good one.
Face it you screwed up - forget it and her and move on, you'll thank yourself (and me) later. Too much baggage and possible BS if you try and steal her back - the new dude is gonna make your lives hell.
"Break the wrist - walk away!"
