I have had a hen that looked like that live to 'tell the story'. Most of my girl's wounds were external, mostly feather loss with a couple of deep gashes. Chickens can get over this external damage remarkably well. Bathe her in warm water to 'flush' the wounds while closely examining her for breaks in the skin. This will go a long way towards soaking out a one-day old infection. After her bath and a very gentle pat down with a soft dry cloth, either rub triple-antibiotic ointment (the type without pain reliever in it, has consistency of vaseline) into the wounds & surrounding tissue or spray her down with an anti-larva/antibiotic spray such as Larvicid (tm) or chlortetracycline spray... any color EXCEPT red on these sprays will be fine.
Chicken healing looks different than human healing. Humans heal best when a wound is kept clean & dry. Chickens heal best when a wound is kept clean & moisturized.
If she has any wounds where much of the skin is peeled away from the meat, consider if you or a vet could add a stitch or two to help the wound(s) heal faster. Do not stitch the entire wound shut, as it will need to drain.
She has extensive wounds, and risks being picked on by the other birds... it's just what chickens do. I recommend that you keep your sweet girl in separate housing (a dog cage will do), where she is still within sight and sound of her flockmates to both ease anxiety and help her maintain her position in the pecking order. Chickens 'forget' their 'long lost' siblings... out of sight, out of mind, and problems can occur when reintroducing if this precaution isn't addressed.
Expect that as the deep gashes heal that her skin will get tough, like leather. That's a scab. My girl's scab was almost black in color, so don't be alarmed. Her plumage may take a long time to recover... perhaps as long as her next molt.
I'll keep you and your feathered family in my prayers.