I'm sorry. She will never change. The violence will only escalate.
Worse, as she grows to know you she will learn more and more how to manipulate your emotions. Saving yourself from this relationship will get harder, not easier.
1) She will undermine your self-esteem and your will-power.
2) She will make you feel that it's your fault.
3) The people who love you and would help and support you will gradually distance themselves from you because they can't bear to see what's happening to you.
4) People will not understand why you stay - you can see it in some of the answers here already. So it will get harder and harder to ask for help.
Save yourself now, while you can, and while you still have most of yourself to move on with. Stay and you will gradually be drained away until you are only a shell of who you are now. You will feel like you deserve no better. You will be afraid to ever try another relationship. Your big heart will be empty and desolate.
She doesn't love you. She needs you for what you let her be. She will never love you, no matter how big your heart or how much love you have for her.
Get away. Spend some time alone to heal and connect once again with who you are.
Take that big heart and heal it. Then find somebody to love who will surrender themselves to you in the same way you will surrender to them.
I'm so terribly sorry this has happened to you. You don't deserve it. It's not your fault. It's unjust that you now have to deal with it. But that's what you have to do. Nobody else can do it for you.
Get away. Walk on beaches. Watch the sun set. Sit in the park. Watch movies. Cry a lot. Do whatever it takes, but you have to do this one brave thing first...