Okay Rynn, here's my opinion:
Girlfriend - Ensure you lay down all the rules and regulations regarding what you will/won't put up with before things get too far. If she's committing you to an expense you don't feel comfortable with, tell her to stick it. If you're slowly finding out you don't have as much in common as you first thought, the harsh truth is it might be time to move along.
Wife - These are tougher to deal with. They're securely in the door and they know it. Once you say "I do" you lose about 70% of your ammo when disagreeing. If you disagree too much, you'll lose about 70% of everything you have owned, own or hope to own in the future.
You can't easily get out of a "wife" situation, but you can handily control a "girlfriend" one. I'd start oozing her to the door immediately. Before long, she'll get the picture. Sounds to me you may not enjoy this coupling as much as you once did and it may be time to do something about it.
HTH
