I agree with TenChicks about there being some dead infected tissue there. I would get some Hibiclens or chlorhexaphine from the drugstore or Walmart, and soak her with a watery mixture of that and wash that area off once or twice a day, trying to get off the darkened skin. It may bleed but just put pressure on it with a dry cloth or pad. Rinse, then apply Neosporin ointment after drying the skin. This should only need to be done until the tissue looks cleaner and more healthy, then only apply Neosporin daily.