My trainer told me to get spray bottle of water and lemon juice. When you catch her chewing, take her to the steps, tell her NO! and spray the water IN her mouth on the roof. She will get the hint that she doesn't like the taste of the wood or punishment. It's harmless. My trainer also said you can discipline your dog anytime as long as you discipline them the day that they did the unwanted behavior. So, take her to the stairs maybe once a day and point to the spot, and then spray her in the mouth with it. I have begun this with my 2 dogs for digging. Seems to be helping.