I feel like a divorce would only make things worse for your mom. Do what otto-san said, and seek medical help.
With the right treatment and time, she could pull through this. You shouldn't just kick her out because of how she treats you. If she has legit mental issues, then you should work towards her recovering. You, your siblings, and especially your dad are probably some of the best people to help her.
Mental illnesses aren't always just purely physical conditions, there can be a lot of insecurities, fears, ect. tangled into it, and those can't really be treated by a doctor (of course, medication can help, but those are band-aid solutions mostly). You have to show her that you guys are supporting her and not against her, that she is accepted despite her issues.
I do sympathize with you OP, as I've had to live through something similar my entire life (sibling with a very bad case of OCD), but please don't give up on your mom. You have to remember that she is ill in probably one of the worst ways possible. I know that living with her is hard, but you have to stick to your guns and do what you can to help her, even if it's hard and miserable.