Valerie I wouldn't be too hard on your sister. Sometimes dogs just act like dogs. When we first got Trevor 9 years ago I had two other dogs at the time. The vet told me when we took Trevor in for his first visit "dogs like to eat what's in the litter box - be careful!" HA! Gross as it sounds, apparently this is very commonbehavior. The cat door has been the answer for us and I know it will work for you too!