Help! Big trouble n Lil' China!!!! upside down in car loan?

My mom is moving out of state to help my grandparents out. She has a cavalier worth...idk...i wouldn't pay more than $900 bucks for it. (its falling apart!!!!) She rolled over an upside down loan on it and it came out to like $17000. (yeah tell me about it....) she still owes like $9000 on it. My bro & i are try'n to figure out what to do to get her out. My bro is a co-signer for her & i'm financing my own truck (not upside down in). I suggested maybe we trade-in both cars/truck get a car/suv/truck that holds its value (honda, toyota) and bite the bullet with that 1 loan. I figured we still be upside down but we would have a better chance at bring'n what is owed down to the value at lot faster than just paying off her vehicle. And we would only have 1 car pymnt and car ins. pymnt. Any suggestions? ...btw she doesn't have GAP insurance!!! :(