You agree to have your sister move in to your home while she divorces her spouse. In the last 7 months, her 80-pound lab chews up and destroys your furniture, shoes, bedding, carpeting, your nephew's toys and anything else he can get, rarely other than while your sister is home and "ignoring" the dog because "he is/was being bad" and she wants to "teach him a lesson." She thinks it's your fault because you shouldn't leave your stuff where he can get it. You think she's an asshole because she's too lazy to get off her ass and actually discipline her dog.
Who's at fault? How would you resolve this situation?
ETA: re: the carpeting & shit, all of the open space on the first floor is hardwood flooring, and only the downstairs office, tv room & gym have carpeting. She wants me to keep these doors shut at all times so he won't go in there and chew the carpet/steal things to eat. Like the ink toner he ate that made him sick, which was my fault for not shutting the door.