Chickens have amazing recuperative powers and many have survived gruesome predator attacks. What is the nature of her injuries? Is she alert or acting dazed (shock)? You can clean out her wounds with a saline solution. and then use Neosporin (NO 'caine ingredients'
You want to keep her wounds clean - make sure she is not where flies can lay eggs in her wounds. The resulting maggots can kill her faster than her injuries. The other chickens would also peck and reopen any healing - sometimes worked up to actual cannibalism.
You can tempt her appetite with anything she loves, maybe watermelon, mashed egg yolk, plain yoqurt, sliced grapes. Keep checking her wounds for swelling, draining, infection etc.
Maybe you could call your vet for advice. or prescription. I hope she is on the mend now.
If you know how the predator got to her please secure your coop or run every way possible. Predators will keep coming back until there is nothing left, OR they cannot get to the birds anymore. Then they will move on to an easier place for lunch.