My heart goes out to you sweety....I went through something similar to this with my Mom (35 years ago) when our family ceased to exist. I know it's hard for you right now, and may be for some time. Even if you can't get your Mom to the much needed help from a professional, don't let it control you.
After many sessions with a counselor I realized I can only control myself. If my parents choose to self destruct, it is not my fault. If my Mother chooses to take it out on me, I know I did nothing, I will not accept the blame.
Be courageous, don't let her take you down with her. Be there for her when she finally comes to her senses, hug her, forgive her then release it.
Most of all, take care of yourself. Get counseling for yourself to give you support and maybe some answers. Hopefully, you have family and friends that can support you.
We're here if you need us.