pipe007, I would lay out your grievances with her before you leave if you think she's worth being in a relationship with. You've been with her for a year so there are other reasons (good reasons) why you stay. Have you ever told her that certain behaviors bother you? That you would like her to not be so pushy and b!tchy? To put more of a respectable effort to make you happy? Or have you just not really said anything?
It can either go two ways: She actually listens, understands and and SLOWLY, over time, changes her negative behavior. I've seen this first hand, but rarely does this happen.
To be honest, based on how she was raised, her education, her friends...I don't see this happening. Her habits are ingrained in her and trust me, she thinks she's right.
OR, she puts the blame on you, stands her ground and says "this is who I am" (which is true) and tells you to deal with it.
Make no mistake; she doesn't want to lose you. She will put on an ACT to keep you around until she's comfortable enough to be a b!tch. Don't let this happen and always call her out.
Personally it seems like this is more trouble than it's worth for you and the negatives outweigh the positives. Give it some serious thought if you want to continue to FIGHT for your relationship.
Trust me, it'll be a fight.
Edit: I had a similar experience with the girl I'm with now. We've been together for more than 3 years and I still think she's awesome. There were issues of trust abuse from her past, and there were also issues on my end. During our time together we always communicated our issues, even though it was really tough. During these talks, we would TRY to be as objective as possible. We liked each other enough to want to change for the better, and I can tell you she's not the same person she was 3 years ago - neither am I. We're more future focused, honest and open minded to listen to each other. She was a heavy drinker and I had issue when I drank too. It's been almost 2 years since we've touched alcohol.
The whole point is some relationships need to mature. A guy like Rollo who already has his sh!t together doesn't need to deal with a lot of the stress relationships have nowadays, money, security, childhood issues, etc. Some people are just f*cked up. It takes a strong person to recognize their personal faults and work on them, for their own sake as well as their loved ones sake.
Does your girlfriend think she's right in treating you the way she does? She probably doesn't think she has a problem.