What should I do if the dog I’m sitting got injured?

The dog I am sitting for 10 days got into an altercation with my dog on day 5. My dog was left with no marks, but the other dog has two scratches on his nose. I refunded the owner for the stay, and I’m continuing to watch the dog for the rest of the stay. The owner said we would further discuss taking him to the vet when she returns. I don’t think I should have to pay for vet bills. Isn’t this why they have the rover guarantee? I’m so worried that I could be sued over this issue, and I am already at a loss by continuing the stay. What should I do? Can I be held liable for this?