It's part of her heat prepping for a false pregnancy, well we hope its false at least since she isn't fixed. Melatonin will help some with the anxiety and out of control hormones. Taking her toys away and hiding them for the time being should help as well. She will think the puppies have died and her body will adjust. If she hasn't had her heat yet you will still have to tough your way through the usual 3weeks but the false pregnancy will shorten with these steps. Once a dog starts having false pregnancies it is likely they will accompany each heat cycle until she gets old enough her heats naturally start to diminish. You have a long while ahead of you. You can either get her fixed, which will stop the whole thing, or get a routine of melatonin, toy hiding, and a loss of appetite around her heats in place. It's fairly common in unfixed females or females that were fixed improperly. Not really worth a vet visit unless she gets extremely out of hand. Some get grumpy. Usually the more disturbing and frustrating symptom is the loss of appetite that can go on for a month or longer.