Hello there and welcome to BYC!
Oh I am so sorry about your bird.
This is very severe and I hope she survives. Keep her under heat right now....80 to 85 degrees. Birds go into shock very easily and shock can kill them faster than the injury. Shock causes great chilling, so keep her warm.
Watch carefully for infection and have some injectable Penicillin G on hand if she starts to shows signs. (you can get this at most feed stores) If she begins eating and drinking by tomorrow but starts to slide backwards in another day or so and stops eating all together, in a couple of days I would start the Pen G injections. You will need to use a 20 gauge needle. Is she a large breed bird? If so, I would get her on 1/2 ml once a day. (1/4 ml for bantams) Inject into muscle only. The breast is the best place for injections. Alternate one day on the right, the next day on the left side of the breast. Medicate her for at least 7 days.
For now, I wouldn't mess with this skin. Let it skin over a bit for today. Then you might use some antibiotic lotion on it. Stay away from Blu-Kote no matter what anyone tells you. Blu-Kote hardens the skin and it will kill her. You want this to remain soft as it heals.
Supportive care goes VERY long distances to save a bird as they heal on their own. They have incredible powers to heal if given the proper hospital set up. So number one keep her very warm. If she chills, she can die. Don't worry about food right now, but she needs to drink water. If you do not know how to tube feed water, dribble a bit down her throat through an eye dropper or even a syringe. Tiny tiny bits at a time so she doesn't aspirate. See if she will eat watermelon. Must birds love the stuff even being incredibly ill. It is all water and this will help keep her hydrated for now.
Keep us posted and keeping my fingers crossed!!