Provide her regular food and grit, not "treats," she needs the balanced nutrition. If she doesn't seem inclined to eat, you can wet the food to make it into a mash like oatmeal, and offer her a hard boiled egg yolk. Check her over carefully for injuries, including her vent and under her wings in case a dog got hold of her.Do you have a dog crate you can put her in and keep her in the coop, in sight of the flock? That way she won't lose her place in the pecking order and have to fight her way back in, and she'll feel at home.