Clean out the wound with water, pour some hydrogen peroxide on it and pack it with an antibiotic powder, like sulfa, or else if you don't have the powder, apply neosporin and let it air overnight. Keep her quiet and calm and dry. Be sure she is able to reach food and water tomorrow. She's probably in shock and will benefit from being left in a calm, quiet, familiar place. I hope she recovers fully and quickly. I've nursed back hens with bad wounds with the above strategy and adding "Rooster Booster" to their water.
I've not experienced raccoons killing multiples in one go. A fox would, coyotes would and dogs would. No experience with weasels.