Don't go to r/legaladvice it's a joke. I don't know if you are in the US or not, but most lawyers do a free consultation. Your best bet is either get her to sell the car to you and take over payments, agree to the terms, or simply get rid of the car and get something else. If you have no records of it going to her, a bank statement of a withdrawal doesn't count because a judge would be unaware of what the money was used for. For example say you have a $400 power bill, you need a cheque or money order as proof because otherwise maybe you just blew it at the bar for instance. Have cheques to use for it, cash app, anything that can give you a paper trail. Consult a lawyer to know your rights and determine what you want as the outcome. If your sister wants it off her credit report, and you want it paid off then have her sell the loan to you or have a written agreement on what you want. Again do not take what I'm saying as godsend just talk and see what your options are.