If you don't have things in common and you are not getting what you want or you are both unhappy, why don't you break up with her then? You will be giving both yourselves a very BIG FAVOUR!!!
Yes, it's given that she is nice & supportive when it comes to finances but a relationship should not be based on that but LOVE...
Questions are... do you love this girl? or does she love you? or is it just the "physical" thing?
