[OwnedByJezebel]

This will probably go away when her false pregnancy "goes away." Some dogs are just very protective with their litters, and since this girl is in her third home in a very short time, she does not know who can be trusted around her "pup." That probably intensifies her need to protect it. Take her if you can, and keep her separated so that she feels safe and protected until she gets through this. If you take away the toy, she will probably either fret terribly because she can't find her baby, or adopt some other object, so just let her keep it.

I don't know if a vet can give her something to short-circuit the hormones and work her out of the false pregnancy earlier, maybe someone else can comment on that.