I'm so sorry this happened.
I consider myself a pretty minimalist dog owner, in all honesty, but think that we have responsibilities for the animals we take into our care all the same.
In your shoes, I'd probably arrange to get the roommate to take the older dog to the vet (assuming you are not able to get there and do so yourself), and pay for it (if the ILs won't or can't).
I might then contact animal services, or I might see if a good foster organization in the area might be willing to take the younger dog, work with her, and re-home her.
It sounds like your ILs basically see the dogs as working animals rather than pets, and given that I suppose I might be willing simply to have both euthanized (if that is the most affordable and safer option, given the situation you describe). But that certainly wouldn't be my personal first choice, if other options are feasible, and that's true even if the other options cost a significant sum of $$$ -- if they (the other options) would in fact produce better outcomes for the dogs.