Well at this point you want to break up with girlfriend yet make her as happy as possible without hurting her feelings. Like when you want to break up with her, introduce her to a boy that she may like and introduce the commons what they are compatable with. And when they are satisfied with that after awhile of meeting tell her that "I can't see you anymore, I hope you understand why I have to go. There is too many things that are coming between us and I set up a bf/gf meeting at [place point of interest here] with the person we met before. He likes you, you like him I hope you have it better with him than me and I am sorry for this but thanks for understanding and good luck with the round 2 (if you know what I mean (no I don't mean 'round' like fat))."
Then you take the time of taking your belongings and leaving the two to happiness and you are happy yourself. YOu didn't cause anyone to be sad. You made her happy. YOur happy. When that combines, you just done a very good thing. (Only problem is if you don't have a secondary option of a girl for yourself. So when you take her to meet the boy that could be her good mate, have your own with too so you don't suffer lonelyness in about a few days after you make the break)
I hope this helps you. This is best option I believe can make good come out of it. I have seen this type of relation before. (11 times actually! ;) That was just little joke there. I got that off of the pie episode of spongebob!