Sadness it can be terrible having an alcoholic in the family, especially one who is supposed to be your biggest support.
Many of us have found out that we can't force an A to stop drinking, even if we tell them how much its harming us, or get angry at them, or beg. In a way it's good to know this because accepting you can't control her, you can start on your own attitudes and coping strategies.
I'm sure she does care for you, but alcohol has it's grip on her and she's incapable of acting how she should. No excuses, but remember she's not drinking at you, she's just an addict. (BTW she either mislead the doctor, very common, or is lying about what he diagnosed).
I think Al-anon would help you get through the next couple of years if you can't find a way to house share or live elsewhere. Continue to look after yourself and limit your contact with her when she's drunk. Keep your head down and survive.
I agree that there might be ways to move out. Why not look into it?