As i said before if you research it you'll see that snake bite frequently causrs necrosis. From your description of her injury it sounds like a bite of some kind.
Sounds like some kind of Necrosis, especially because of the smell...that's horrible. I don't think it would be bruising but hard to say since you don't really know what happened. I wonder if what attacked her could have been something venomous, (with some kind of slow acting venom maybe not...