13 yr old Black Lab Unable to Eat and Hold Down Regular Dog Food

We have a 13 year old black lab who has digestive problems. She is unable to eat and hold down regular dog food, so she eats a diet containing eggs and baby food. She is able to hold that down fine. We are wondering if there is anything else we can feed her to keep her strength up without taking too many risks in "experimenting." We do not want to damage her already compromised digestive system. Do you have any suggestions?