Legal help. I ran over my neighbor's dog and she is threatening to sue?

Okay so here is what happened. My neighbor has this little dog that is so annoying. It is always at my house pooping in the yard, and she may or may not clean it up. It even runs in my doggie door and eats my dog's food. I hate that dog, I admit. It has fleas, and is just so ugly and annoying. Maybe like a shnauzer or something like that... I tell her all the time, get the little mongrel off my yard and she just takes her sweet time. On Monday I was running late for work and that dog was under my car. I honked and it wouldn't come out. Not being afraid, just being stubborn. I knock on her door, nothing. I finally call her and leave a message saying her dog won't get out from under my car and to come get it or I will be late for a store meeting. She finally called me 10 minutes later saying she would be over... I waited 10 more minutes trying to push it out with a mop, but it would move just enough to get away from the mop and climb back under growling at me. So finally I just get in my car and honk again, and nothing, so I put it in reverse thinking it would surely move, but it didn't. I ran over it and now it is all screwed up with like $2000 worth of vet bills or something. I mean this is so stupid. I hate that dog, and she is just in the wrong. What can I do to get out of this?