Sorry to hear you are going through that stress. You are on the bettering board, you might consider the
conflicted or breaking up board to get some better thoughts about where your head is at as well as untangling finances.
But that being said, If you go through with what it takes to separate from the loan (see below), I imagine that will be a betrayal (as far as the exBPD is concerned) that will be difficult to come back from as far as reversing the breakup, if that is your ultimate goal. In my opinion this should only be something you are doing if you are really ending this thing(relationship) for good. How do you feel about that?
My approach might be, "hey I won't leave you in a lurch here, I can make (insert number) more payments and during that time I need your cooperation to resolve this and transfer ownership of loan to you. If we can't get that done by then, in order to protect my own finances I will need to (insert something from list below)"
If you are on the title as the owner or the primary on the loan, you have more options. Could even sell it without her depending on state if you are primary owner. Depends on state/country
You might be able to get a cosigner release. Some loans have a program that will release a cosigner’s obligation after a certain number of consecutive on-time payments have been made. Two years of on-time payments seem to be the norm. Read through your loan documents to see if there’s any type of program associated with your loan. Or, call the lender and ask if something like this applies to your loan.
As far as the car you are left with this:
-Refinance the loan
-Sell the car (have to pay remaining balance)
-Trade in the car or sell to dealer/carmax (have to pay remaining balance or roll into new car) You could also double trade, your car and her car into one new car. Might make it more financially viable, might make it worse.
-Keep the car, make the payments, and pay it off
-Let the bank repossess the car (have to pay remaining balance)
-File bankruptcy
https://www.accurateautoadvice.com/credit-and-financing/are-you-co-signed-with-an-ex-boyfriend-or-girlfriend/Good luck