Not near enough detail to tell. If you want a legal opinion you need to talk to a lawyer.
The key thing to remember about a short sale is that the seller does NOT WANT TO SELL, the seller HAS TO sell. If the seller can figure out any way to keep the house, they will.
Pragmatically, the seller in a short sale needs to take numerous actions in order for the short sale to be processed. Pretty easy for them to not take an action and have the sale fail. Sorry, but it's time to move on to the next house.