Foods that have not been highly processed are the most assimilable for a cat’s body. The best food for most cats, regardless of age, is fresh food. http://healthypets.mercola.com/sites/healthypets/archive/2016/05/09/feeding-older-cats.aspx
Your senior cat is very much like an elderly person in that she has important, specific nutritional requirements. She may no longer have all her teeth, or she might have frequent difficulty with digestion. Making fresh cat food at home might be the answer to better health for her.