is she showing any signs of breathing problems? cough? sneeze? gasping? Make sure she has access to plenty of clean water. if you have or can get some chicken vitamins, it would be a good thing to give her a dose of/add to water.
I would keep her in clean/dry bedding, if possible. You could soak her for as long as she tolerates..... my chickens actually enjoy a good foot soak. I would just be sure after you soak the foot to pat dry and apply some lavender oil.....
i use pure lavender essential oil for skin/feet problems in my girls and have had success. i apply it directly to wound at least twice daily..... you could do a soak using warm water and a few drops of oil, then pat dry and apply some of the oil to the area.