I had a few paragraphs worth of response to your original post when I reread it again and something really stood out to me - how do you really feel about your girlfriend? You don't have to respond, I'm just asking rhetorically.

If you're willing to end the relationship just because she wants to get married and she's not willing to put any work in unless you do get married, it sounds like it would be unfair to both of you to stay together unless you have some sort of long term idea of where you want your relationship to go.

It's really easy to get caught up in the status quo - we as people don't like change and will tolerate some pretty surprising things just to prevent it. I've been in a relationship where we didn't agree on major topics like marriage and kids, but we stayed together because it was the convenient thing to do. I think we both hoped that something would change, but inevitably were apathetic to that end because we were on "relationship cruise control". Now, I'm happily married (to someone else) and in retrospect, I'm glad I ended that relationship. My ex is also happily married and has a couple of kids. It worked out better for both of us to just end it.

I'm not one of those feel-good people that's always going to tell you to work it out. That's why I asked you how you really feel about your girlfriend. Sometimes, it just makes more sense for both parties to move on.

Best of luck to the both of you.