So far, so good. I've seen much worse on this forum that I insisted could not possibly survive. If you haven't already, you need to treat her with electrolytes to ward of shock and dehydration.The biggest risks are infection and dehydration. Keeping the wound clean and moist with daily cleansing and debriding if necessary are required. It can be grueling since it will be ongoing for six weeks at least.
Do you know a nurse friend or ER tech who could stitch her up? Or, wait for it... a vet? With such a large wound, it would be nice to accelerate healing by either a flap of skin as a graft or stitching the wound mostly closed so healing won't take so long.
Without closing the wound up to reduce its size and the new tissue replacement, you will be facing daily care as the new tissue grows inward from the edges toward the center, much like ice forms on a puddle.
Also,with such a large, raw wound, she will need to be segregated to keep her safe from the wound being pecked by the others. If you can rig up a temporary infirmary enclosure in the coop or run so she can still be part of flock life, even though peripheral, she will be much happier and heal better.
One other thing you can do is try to cover the wound with gauze permeated with antibacterial topical ointment much like they do with burn patients with large raw wounds. This can reduce bacteria and keep the wound clean and moist. One other little tip. If you have any of those stretchy orange bags clementine oranges come in, you can use that as a body stocking to keep the gauze in place over the wound.
Another great product for large wounds is Silvadene burn ointment. You need to have it prescribed, though. The stuff is simply amazing as I experienced years ago when I was burned badly in a fire, and later when I used it on a baby chick with a scalp wound. The healing is very accelerated with this stuff if you can wangle a prescription out of a doctor or vet.
While you're at it, it won't hurt to get her on an oral antibiotic such as amoxicliiin. This you can buy online from animal vet supply outfits under the category of fish mox. 250mg once a day for ten days. Or ask at pet stores and feed stores.