I mean be aggressive when you talk to the debt collectors. Say, "Look, this is my mother-in-law, and I'd like to resolve this situation if I can. The thing is that these fees are ridiculous. If you can knock it down to, say, $4000 total, then I can step in, pay on her behalf, and we can walk away from this. I love my mother-in-law, but she's still an in-law, you know? So if you guys aren't going to work with me on this bill then good luck - go ahead and see what you can get from her. She doesn't have a penny to her name."

It presents them with a stark choice: they either get money from you in settlement of the debt and walk away, or they get to try to file an expensive lawsuit against someone who is judgment-proof (i.e., has no money anyway).

Obviously, I don't know the details of the situation but I think you have serious leverage if you use it properly.