They could give some IV fluids under her skin if the rescue center has a vet. If the part of the comb is just hanging, they may want to remove it, especially if that is the origin of the bad odor. Tube feeding could be done using a section of aquarium air tubing (Walmart or a pet shop) or oxygen...
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...