If she was rescuing them, it’s very possible that they had previously been abused, and may have been raised to fight.
I’ve read too many accounts of pit bulls raised by normal people “snap” and kill their owners or someone else to place much hope that this dog’s behavior can be explained away by abuse. It isn’t known if she was rescuing them or not. Pit bulls are commonly given up (shelters or the street, where they become someone else’s problem) when their owners discover alarming levels of aggression in their adorable dog they raised from a puppy.