Unfortunately I know a woman like this.
Adopted a dog she said had "behavior issues". Few months later without warning it bit her sister on the leg so bad it had to be pried off. Hospital visit for the puncture wounds resulted in animal control notification where she found out the dog had previous bit a child and had a file stating the dog should never be around children. That's when she found out the sister knew this already and didn't warn anyone. Owner showed no remorse for the bite and kept saying it's a good dog.
Couple months later it nipped her other sisters boyfriend. Then nipped the contractor who came to give a home reno pricing. Still no changes, owner continues to only care about dog, saying it must be everyone else's actions around the dog and people should act in a certain way when in the same house as this dog (these were all unprovoked bites, not an attempt to pet it and it nips, the dog literally came into the room and bit without warning).
Last week the dog bit a neighbour on the leg ripping through her jeans and causing injuries, while she was holding her new infant child. She's still defending the dog and logic just isn't sinking in. Pretty sure animal control will be demanding the dog be destroyed now, finally.