To update: so far, we seem to have avoided any further action. Besides immediately paying the woman's vet bills and dropping off a small gift card for her to treat her recovering dog, I stayed in contact only occasionally, via text, to see if her dog was, in fact, recovering well. She was gracious and the dog had no setbacks and has now had her stitches removed. The "victim's" owner was very kind and was grateful that I was concerned. Admittedly, I was almost as concerned about being sued and my dog being labeled or taken as I was about her dog's health but, as a dog lover, I *was* genuinely concerned about her dog's well-being and made sure to convey that.
I got lucky this time. I am now very careful where I walk my dog, who is around us, and am considering muzzling her and maybe walking the 2 dogs separately.