I agree with Dunster.
Yelling at the dog does nothing except teach the dog to be sneaky and only chew when people aren't around to yell.
Tell your niece to go to the grocery store and buy fresh habenero peppers at least 10 of them. Cut them in half and put them in a quart jar. Fill jar with vinigar. Let concoction steep for several weeks. Get a spray mister bottle and mix half the hot pepper vinigar and half water. Spray anything she doesn't want chewed. Be careful when spraying this stuff is hot, hot, hot and can cause you to cough while spraying. It won't harm any surface. You can put it on wood, upholstry, blankets, shoes, etc. Give the dog appropriate things to chew such as raw beef marrow bones, Bully Sticks, Kong toys stuffed with treats. The inappropiate chewing should stop within weeks. Re spray any surface as needed. Do NOT spray this stuff directly at dog or any person, it is basically pepper spray that could do serious harm if gotten into eyes or mucous membranes. Only give this recipe to your niece if you know for a fact her kids won't think it is a fun idea to spray someone or any living thing with it. To be used only on surfaces you don't want the dog to chew.