I guess the question now should be, is that the type friend you want to have? Are you going to remain friends after this? Quite frankly, she sounds like the type of "friend" you would be better off without. That being said, I would only pay her if you plan on continuing the friendship. BUT, if you don't plan on remaining friends, then I would simply tell her that after consoluting with a civilsuit attorney and the sheriff's office about the situtation, you have decided that you are not liable for any of the vet bill. Let her know you are serious about the situtation and have already consulted attorneys and the law. Paying half the bill is kinda like admitting fault IMO.

That is a pretty large sum of money to basically throw away because your "friend" doesn't have the common sense God gave a cow! I could think of many better ways to spend it. As I said just my opinion.