
It definitely sounds like a phantom. Almost all bitches suffer this to a greater or lesser degree after every season, whether or not they've been mated. Some have almost no symptoms, others go the whole hog, nesting and producing milk, and can make themselves quite ill.
Take away all her toys so that she has nothing to 'mother', and make sure she doesn't go all broody and mopy, curling up in a quiet 'den' - you may even have to take away all her bedding to stop her nesting. Cut down the protein level of her food and keep her very busy and active - be very public school, no-nonsense!
:)