Her being a vegan, you think you'd have realised that meat isn't her thing, really. Cooking it/handling it is against her newfound ethical beliefs. Basically, she doesn't want to be cooking dead animals. That you'd say that her not cooking meat is 'selfish' is in itself a selfish thing to say. Really, I don't believe that you should be in a relationship with her if you'd think about breaking up with her over something so petty. Getting protein in your diet isn't hard, even as a vegan (admittedly it takes more thinking about), I think you should just ask her to consider making more protein rich meals for you. As suggested by others, there are a multitude of ways that you can continue to include meat as a part of your diet (slow cooker, frozen pre prepared meals etc), you might want to actually talk to your girlfriend about this though, and see what she has to say about your thoughts.