Sounds like sister and dog might do well with some good dog obedience
classes. There are good ones around. I have lived with dogs for thirty
years and no way would I put up with that.
My puppy has his own chair in the living room but is not on the other furniture and does not chew things except toys of chich there are many. Have lived with a slipper chewer though for a brief period and know how annoying it can be. Sure made me pick up my slippers, put them in the bedroom and keep that door shut against the puppy in daytime.