Do you cook parts of the food? Sometimes cooked foods work better for certain animals. You could also add more fat to the diet to increase the caloric content. I advise owners to give digestive enzymes to their pets to aid breakdown of the food as well as probiotics. German Shepherds may need pancreatic support. I would also give H20-IonX to aid utilization of the nutrients and improve digestion.
Have you had your dog checked for parasites, a stool sample checked for fat digestion, and has she had any blood work done? Looking forward to your response.