Please do not feed your dog grape juice, grapes or raisins as they are toxic and some dogs get kidney failure from ingesting grape products. It is better to make sure your dog eats fiber-rich food (you can mix canned pumpkin into her regular food, not pumpkin pie filling) and make sure she exercises a lot. Take her for a long walk, which will help with eliminating. If the constipation does not resolve she will need to be seen by a veterinarian who will give her an exam trying to find the cause for the constipation and possibly an enema especially for dogs. he may also prescribe medication to facilitate elimination.