Avoiding by-products and artificial preservatives is the minimal standard for good nutrition. Feeding organic foods is even better.
In human nutrition, processed foods are considered by many nutritionists to be inflammatory. The same is true of pet foods, especially Kibble. Recently, concern has been raised about the heavy metal (lead, mercury, arsenic, etc.) content of commercial pet food. It has even been suggested that if one chooses to feed commercial pet food, adding detoxification supplements would be a good idea.
Because of these concerns I recommend feeding home prepared food made from ingredients purchased at a grocery store. In order to ensure an optimal diet, I also recommend adding a good multiple vitamin and mineral supplement.
Feeding home prepared food can be less expensive than commercial pet food. You will also probably find your pet has regained her lost appetite. When food tastes good, eating is one the pleasures of life- both for people and pets.