I cosigned a loan for ex, now looking at repossession...?

I cosigned on a loan for my ex to get a car. We split up two years ago, the original loan amount was $20,000. I just got a letter in the mail saying that if I don't pay what's owed, which is $900, by the end of the month the vehicle will be repossessed. The total amount owed is $14,000. In the past year, I myself have paid $1,500 in payments towards the car to keep my credit good. However, now I've been doing a bit of reading and it's my understanding that if the car does get repossessed, it gets auctioned off and the blue book value for this car is only $6,000. So even if it was to sell for blue book at auction I'm still looking at the rest of the loan plus fees. I repeatedly try to get in contact with my ex.. she will not return any of my calls. I basically just want to know what my options are... Ideally, I want to be off the loan. I'm not on the title, just on the loan. I'm pretty sure there's no way to just get off the loan without her refinancing or something, but she's obviously not willing to cooperate. What are my options? The car was obtained in Maryland, and is currently in Maryland with my ex and I live in South Carolina. Thank you so much for any help!