Disabled with Sallie Mae loans

My mother has co-signed numerous private student loans for her children, myself included. I am in repayment and have been on time with the loans but we are having an issue with my sister who also had my mom as a cosigner. She graduated 5 years ago and unfortunately was in a car accident (she was not at fault) shortly after. Now she is registered as disabled; she can not work receives social security and is hospitalized twice a year to get treatments for Complex regional pain syndrome. She was on time with all her payments until this accident happened and my mom paid her loans for the 3 years after but just can not pay them anymore. My mother went back to school and currently has her own student loans to pay back. Whenever Sallie Mae calls about my sister's loan my mom gets transferred from one person to another and every time she is on the phone for at least an hour and receives different answers, yes they have programs for the disabled we will send paperwork, no they don't have programs, they don't even know what they have. Sallie Mae is trying to garnish her wages because she was a cosigner for my sister and they know that my sister will not be able to pay them because she'll never be able to hold a full time job. My sister was not disabled when she took the loan out, she will in no way be able to use the degree she had taken the loan out for and she was consistently paying before her accident. There has to be programs for people with unforeseen circumstances, is there anyone out there that could help us out as to what rights we have and is there person to contact (lawyers, politicians, ect.) that could help. I am sicken to my stomach that I am paying 12% interest rates for my student loans from Sallie Mae when they can't even give my family a straight answer. We have been waiting since May for these supposed papers and have to deal with them harassing us while they refuse to deal with the issue at hand.

All responses are appreciated, thank you for taking your time out to help a family in need.