Poor thing! Give her a nice warm dark quiet spot so she can recover. If you've got towels you don't mind either washing or throwing out, use them to line the bottom - you don't want to have her kicking bedding or other particles up into that wound.
As much as you can, trim the feathers around the edge of the wound - if a trip to the store is in order for wound supplies, grabbing a small curved pair of sewing scissors is a handy thing for getting in close to the skin without risking poking her. (
https://www.walmart.com/ip/Fiskars-4-Orange-Curved-Scissors-1-Each/34932916 )
You won't want the feathers matting to the skin as the healing process proceeds- it will just make a gooey mess- and naturally the feathers have all sorts of stuff on them. I'm a fan of Vetricyn - usually found at farm supply stores - it can work absolute wonders. It is pricey, but - a little goes a long way. It doesn't burn healing flesh like hydrogen peroxide can- hydrogen peroxide is good for an initial flush of bacteria, but not for ongoing treatment.
In cleaning it, if she will tolerate being put at an angle that will let any potential pooling moisture down in the wound to drip out- just barely beyond vertical. Given that it's a dog bite and the bite is fairly deep, I would probably avoid stitching up.
I hesitate to recommend aspirin for pain relief just yet until you know there's no further bleeding. Aspirin is a blood thinner. BUT - if you're headed for the store, pickup the children's chewable aspirin - the adult stuff tastes terrible, but the children's chewable ground up (a pill crusher- usually by the pharmacy counter, comes in really handy). Sprinkled over a favorite treat- watermelon, cantelope- I've never had one refuse it.