My Mom Is a Drug Addict and Needs Rehab Badly?

My mom is 56 years old. Before all this started she was a happy normal successful woman. She worked tirelessly to help support me, my brother and my sister. She kept a spotless home and drove me out of state every weekend for gymnastics meets. My dad had a pretty tough job and worked long hours so it was mom that did everything for us. Things were great until I got to be about 15. My dad lost his job and started doing hard drugs. They’d always smoked pot but I’m talking about meth and cocaine. First it was a little here and there and then it got to the point they were both addicted to meth. My older sister was already out of the house. Neither of them were working, my dad had several little bullshit jobs here and there but he could never keep one for longer than a few months and whatever money they made went generally right to their drug habit. Eventually I moved out of the house at 17 just to get away. My brother was 14 and too young to do much about it so he got the worst part of it. We were never hungry or abused or neglected. They just did a lot of drugs and things were really crazy, I remember fights that left huge holes in the walls and lots of threatening divorce. Fast forward to now, that was about 8 years ago, they have both calmed down but have turned to prescription drugs instead. My mom is on so much medication for depression, fibromyalgia, she’s on anti-psychotics, you name it, she’s on it. My dad still drinks and takes stuff like Xanax ‘recreationally’ but it’s no longer the party it used to be. Mom is no longer able to care for herself, I really think her mind is just gone from all the drugs and stuff they did before and the pills just pushed her over the edge. She is no longer able to care for herself, my dad says he has had to wake her up and change the sheets and her clothes because she has used the bathroom while in bed. She cannot cook or do chores or even dress herself. I haven’t had a real ‘mom’ for a very, very long time. Today he called and told me he found her wandering outside in the road barefoot. I am 22 starting out with a new family of my own, we have a 2 year old and one on the way. My sister is 33 and has 2 daughters of her own, she is married as well. My brother is 18 and is headed down pretty much the same path our parents went. Dad informed me today that he was tired of caring for her and wanted to move out of state with his mother. He said “she can go live in a home or something.” My sister has nothing to do them, my brother is obviously useless, and I live out of state and am not in a financial position to really do anything. I don’t know what to do. I’m not sure if it’s just the medication she’s on now that is doing this to her or if her mind really is gone. I kind of have come to terms with the fact that I will never have my mom back. But I have to do something, she cannot care for herself, and I really think my dad would just up and leave her. I asked him if she would be able to care for herself and he said he wasn’t worried about that anymore. What can I do? How does rehab work, since she is over 55 does she get any kind of gov’t assistance? How would I even go about starting this process? Please help me. I don’t know what to do and I am scared for my mom. It seems like everyone but me has forgotten that she gave us the best years of her life being a good wife and a good mom and now she is just some crazy lady that is a burden on everyone. I appreciate any advice.
Please understand, her mind is gone. I doubt she even has competent thoughts.