None of us here are doctors. This board is for peer-support.

I don't know much about the topic in question. I do know that brain injuries can vastly affect memory though, it's possible that she really believes she's telling the truth.

As far as getting her to stop blaming you? Good luck with that. People who firmly believe something as truth will generally not listen to any amount of reason/logic even if the belief in question is blatantly false. My advice? Change how you view the situation. You can't change other people, but you can change yourself and how you choose to react to her accusations.