All I can quote are the laws applicable in my state.
Being a cosigner I am sure both names are on the title. That makes it impossible to sell unless you go thru small claims court and sue or get the required signatures from all concerned. The vehicle will be repossed if payments are not made. This may damage your credit standing but that may not be too bad if that is all that happens. Seek assistance thru Senior Citizens Groups. They may provide a lawyer for you.
For future consideration, Never lend money (or cosign) for a friend. Don't even talk about this with a relative. If their credit is bad enough that they need a cosignereven though they both have "good jobs" tells me a lot. I have told relatives and friends that if I cosigned with them they would have to put 99% as a down payment and finance the rest. In easier way out but we all have to take drastic measures from time to time to save our own skins.
Sorry for not being of positive assistance and I wish you well. dp
