Give her sugar water to help with the shock. Keep her warm, and if you can, inside your house. Trim away all feathers that when wet OR dry will lay into the wound (you don't want feathers dipping into the wound).
Vetricyn (the all-animals kind will do just fine, it's twice the volume for about the same price as the "poultry" formula) will not hurt like hydrogen peroxide and alcohol ... and can be used throughout the healing process.
Aspirin- as long as there's no bleeding - can help with the pain. I use the 81mg chewable (cherry) "low dose" aspirin. I crush it over whatever the hen will eat, or if you know how to tube feed, you can do it that way. 81mg treats 3lbs of bird, so if she's around 6lbs, 2 chewables per day. I like them because it's a lot easier than messing around trying to divide a 325mg pill into the right dose. Tastes better too!
Nutridrench for poultry can be helpful to bridge the gap if she's off her feed for a couple days.
If she won't eat/drink willingly from dishes, use a syringe. 12cc is a good size. While you can force the beak open and "syringe" them, I like to just lay the tip of the syringe at the corner of their beak and slowly dribble fluid in- like greasing a hinge. Don't force the head up or back- it may take some tries, but they catch on to capturing the fluid and swallowing it down usually- and you won't have to fight with her to get it down that way.
Scrambled and/or hard boiled eggs ... her normal food made into a mash with warm water - and generally whatever treat she'll accept.
Wound treatment - After the initial cleaning, spray with Vetricyn then slather on antibiotic ointment to keep it moist.