My Son Bitten at Sitter's Home, Am I Liable for Medical Bills?

My son goes to an in-home licensed daycare. Everything has been great so far, except one thing. My sitter has one indoor dog that is very calm and used to children. She also tends to take in strays but they stay outside the home and the fenced off play area. She had one of the females spayed and kept her inside to keep it away from the male dogs as the vet instructed. Problem is, my son (he's 3) tried to pick up the dog and it bit him on the nose/face. (It was on the living room couch.) I was at work, so I woke my husband up (he works nights) to take my son to the dr. My husband thought the bite might need some stitches but was not severe so he took him to urgent care. They said the bite needed to be sewn by a plastic surgeon to ensure it was done straight, so they sent him to the ER. My husband took him there and I met him there for the stitches. It was time consuming and very horrible for my son. I got a $35 bill for urgent care, a $50 bill for the ER, three $20 bills for the follow-ups with the dr, and the medicine brought the total to $220. I paid the bills, and brought the bills to my sitter's attention just before Christmas. I told her that it was a bad time to bring it up, but it is a hard time for me too. She acted shocked I would even think she should pay anything, but said she would let me know what she could do. I haven't heard anything since. She is a great sitter otherwise and the only one I was able to find so I don't want to lose her, but what do I do? I think she should pay for all the bills, it is the least she could do since my husband and I both missed a full day of work. My younger son stayed at the daycare while we had the older one at the hospital and we didn't get reimbursed for the day of daycare either! At least I'm not suing like everyone seems to do nowadays!