We live out in the country as well. Unfortunately people outside of the city tend to just turn their dogs loose, so really all you can do is make sure that your dog is not loose from you. I personally would never let my small dog off a leash when outside. Out here everyone owns hog dogs and other hunting dogs that are all out wandering free and they would probably look upon a small dog as prey.
If you could find the owner of the other dog you could try telling him about the incident, but I wouldn't expect a very positive response. I would suggest that the guy consider neutering his dog, but probably the guy is just going to tell you that that's your own problem and get off his property. I am almost 100% sure that he won't offer to help with your vet bills. I know that out here everyone is a jerk about their loose dogs and just find everything they do funny.
I'm sorry that your dog was injured.

I hope that she recovers completely. I think that you should spay your dog and please keep her on a leash close to you when you take her out on potty breaks so that if anything else ever happens you'll be right there to stop the event before it happens.