It is hard to know what has happened to her. A predator could have injured her head, but it would be just a guess. With her eyes closed and swollen, I would flush them with saline, and twice daily apply either Terramycin eye ointment from the feed store, or plain Neosporin. Those can also be used on the head wounds, though I would use Neosporin on the skin and comb. Try to look to see if her eyes are intact. If you can lift her up, and see if she can put any weight on her legs or balance. Feed her several times a day using chicken layer feed mixed with water. You can also offer some dry crumbles as well. Scrambled egg is a good treat. If she cannot stand, then a chicken sling might be good to get her up and near food and water.