If she can't admit that what she did was wrong yet blames you and is holding that punch over your head, I think its time to take a breather. I don't think there was anything wrong in what you did given that if you didn't fight back you may very well be dead right now.....has that thought crossed your mind? Her actions could have killed you if you didn't fight back! Yes, it was right of you to apologize in an effort to patch things up between the two of you, but if she can't own up to her end of what happened, its time to say goodbye to her. In my experience, these types of people take no responsibility for anything and their actions are always justified by what the other person has done. That is, everyone else is to blame.

How well have you really gotten to know her? I am all for living with someone before marriage as it allows you to see them in all of their glory, and not just when they're at their best. I've seen this happen far too often. I had a friend date his soon to be ex wife for 7 years and it wasn't until they got married did he realize just how incompatible they were. Seven years of dating and they didn't realize the incompatibility because they didn't live together or stay with each other for more than a few days.

ETA Maybe she should be THANKING you for fighting back? If you just laid there like a wet rag and she did choke you to death, she could be facing murder charges right now. Seriously.