
I would think the vomiting is caused by an emty stomach, not the phantom in itself. Try giving her something to eat that she likes, if she won't eat her normal food, just to avoid a totally empty tummy.
It's very common for bitches that are having a false pregnacy not to eat. One of my girls will not eat her food for about two weeks, but will have little bits of chicken, scrambled eggs or rice pudding. Don't worry, your girl sounds perfectly normal, and you'll learn to recognize the symptoms after each season.
Karen