Not long ago a friend of mine came to me with a situation she needed to have explained. She had been watching one of those judge/courtroom programs where the TV judge decides who owes who what.
This case involved a young adult dog that was purchased from a breeder then driven a couple hours to its new home. The drive home was uneventful, but the dog panicked when it arrived and realized that it wasn't in familiar territory, and there was no other dog there to take cues from. (remember this was a kennel raised dog and had never been in a single dog environment) The dog hid under furniture for days and would not come out for food or potty, would not allow the new owners to get near it or touch it. The new owners returned the dog to the breeder saying there was something wrong with it.
My friend wanted to know if I thought there was really something mentally wrong with this dog, or what....how strange did this story sound to me? Actually, I hear similar stories of dogs in stressful situations like this on a regular basis. It isn't always from being sold or given to a new home, sometimes it is from a favorite family member (dog or human) leaving the household.....sometime it is from the whole family moving into a new house....this kind of behavior, although not always as dramatic as the TV story, is common for a dog that is in emotional stress.
We recently/suddenly lost an old Golden Retriever to cancer. Brown was the companion dog for our equally old, blind and deaf Cocker, Molly. For weeks after Brown died Molly did not want to eat, we had to beg and hand feed her. She stayed in her dog bed not socializing with the rest of the family, which was very much not like her. About the time we thought she surely must be deathly sick, she started to return to normal and is now fully adjusted to her life without her dear companion.
It does take time, work and compassion on the owners part to help a dog through a stressful time of adjustment. The more you know about a dog's past lifestyle when you adopt or take in an adult dog, the easier you can make the adjustment by trying to avoid drastic changes at first. You may also need to seek out professional help either from your vet or a training instructor. Just try to keep in mind what the dog is going through and that it will take time and effort on your part to help her make the adjustments necessary to be a wonderful family member in your household.