My 72 year old mom just lost her home to bankruptsy, (elder loan prey) and moved in with my brother. She gets about the same amount as your mom. Her prescriptions are appx. the same as your mom's. All but 3 are generic, but those three cost a bunch. My sister contacted the Dr.'s office, got paperwork for free or reduced medication from the corporations that make the drugs. Now she gets all three of those meds for free.
You should have a lawyer draw up papers for you to be her power of attorney, go to her, with a witness, have her sign the paperwork, then switch her SS to come to you. You can buy her meds for her, give some "rent" money to your sister, and use the rest for your mom's clothes, hair, and other things that will boost her morale.
You are right; there are other places that will care for your mom. Her housing sounds unacceptable. I would follow Will's advice.
Praying for you both