Can you get some more photos, it's hard to tell where that is on the body.
Where are you in the world? What's your temperatures like?
I'd move her to a separate area and begin working her through shock.
Sugar water or electrolytes as suggested are a very good idea. This will help keep her glucose levels up. Chickens will try to act perfectly normal even when severely injured.
If you have Hibiclens (Chlorhexidine) use this to swab the wound clean. It's very deep, so I would be hesitant to flush heavily, just swab and clean very well, trimming feathers away and out of the wound as you go. If you don't have Chlorhexidine (or similar), then you can use Saline. Do the same - swab the wounds until we can see better and try to gauge how deep that.
Once thoroughly cleaned, apply a thin layer of triple antibiotic ointment.
Often an antibiotic is not needed, a bird can heal well on her own, but if you have an antibiotic on hand, I'd start it.