I'd make it known far and wide how much damage her dog has done, complete with pictures. I'd start with Facebook, let any other potential suckers know in advance what a terror her dog is. You would probably never see your money back if you boarded the dog, but it just might be worth it.

NEVER AGAIN. I'd tell that friend were to go if she asked again.

Just start posting their bill.

This idea may be rash but what the hell? Update your friend and pretend to put the dog hostage and that you'll kill it until your friend answers the phone.

you deserved it. you agreed to take of the dog. don't "lawyer up" because you won't get anything, only humiliation.

Take it to a clinic and have the bill sent to your friend

I watch my parents dog. Often. And for days. I can only take 4 days in a row before I'm ready to kill it, and their dog is decently behaved. You need to find a good kennel and board the dog. Then never dog sit again. Lesson learned.

Post on her wall that her dog is destroying your house and if she doesn't answer your calls, you'll put the dog in a doggy hotel and leave her with the bill.

Record all the damages (pictures or videos is best) and request her to pay. If she doesn't maybe small claims court might be an option. I don't usually suggest this but it's not like the dog broke a cheap lamp or something. Furniture is a lot to replace and so is vet bills if your dog was injured from the attack. Maybe the dog is nervous. Not its fault :( I hope your dog is okay! Contact her other friends or family to try to get to her if you can. She can also get into big trouble for negligence of a pet. I'd make sure she knows that ;)

Make a facebook post and tag them in it letting them know that their dog is at x pet hotel.