You can teach a dog not to attack your chickens. When we first got chickens that is the first thing our dog did was to kill one. For at least a week after, I would take her out on a leash every day, show her the chickens and the barn, and tell her sternly "no no no". Sometimes I would reinforce the nono's with a rolled up newspaper. She did get the idea that she was not to attack them. In fact, she became their protector, and we used to call her a Chickherd (instead of Shepherd) lol because she came to look at them as her friends. I know that this might not work with all dogs, but it's worth a try. She died a few years ago from age, and I've been reluctant to try another dog, but we probably will eventually. You could also try a shock collar for the dogs.
So glad to hear that your hen is eating! Good for her. And you!