A lawyer is the best option. I've seen that unfold several times to people around me. The chick winds up not paying the bill (since her credit sucks already) and the guy winds either paying the bill or becomes the recipient of bad credit. One person I know went through bankruptcy partially due to a car(although in reality his debt was around $200,000 and the woman's car only accounted for about $30,000 of it). The laws in the US are about to change for bankruptcy so if you live in the US, look into this soon. When you co-sign, you agree to pay if the other person defaults. If your lucky, talking to a lawyer might scare your ex into making sure that a non-payment is due to actual financial hardship and not revenge.