NO! It is not your fault! My first feeling is that she is using this idea to manipulate you and pull you further into her problem because she feels abandoned. Another part of me thinks of how she is grasping at straws trying to find a way to make herself feel better and this is one way that has helped other people feel better for the short term. What makes me angry is how she turned it on you when she should be going to get help like you have suggested. She is making the choice not to seek help AND putting you in an awful position. Have you thought of telling her that you don't want to cut and if you had a choice to quit this habit right now you would? And how you are getting help to stop cutting and it would be easier for her if she got help for her relationship trauma NOW instead of cutting and then having to get help for that AND the trauma too? Remember this is her choice. Your telling her about your problem didn't MAKE her do anything. She is choosing to do it.
Carrie

PS I have had a friend cut after I told her I had a problem with it. When I told her she got all over me with the whole "you already hurt enough, you shouldn't hurt yourself more" bit. Then she got into a rough patch and cut herself. I got angry at her. It seemed so hypicritical. On the bright side she hasn't cut again. It didn't satisfy her need like it does for me. I don't know why this is. But it doesn't work for everybody.
CK