Well, sorry, but if you don't have the will power to split up, then there's nothing you can do.
The only advice i can think of is, if you really can't split up with her, get her to split up with you. As you said, you aren't close, so you know what she won't like. better yet, if you know what she does like, and you have a friend who feels something for her (happens more than you think. just ask them) then tell them how to make her like them.
Or you could bite the bullet (I hope that metaphor works. I never figured out what that one actually means) and try to break up with her. Take Alexstrandberg's advice.
'If you decide to leave your current girlfriend the one issue you might run into is guilt or obligation to stay with her. You don't owe anyone anything. It's best to cut a relationship short when it's clearly not working than to drag one out for months making both people more miserable. '
I hope this helps.