Do you bath her yourself? I would suggest a good high quality shampoo and conditioner for her skin. If you search shampoos on here I am sure you will find a lot of suggestions for good quality shampoos and conditioners.
You could also try Missing Link Supplement which you can get at Petco or Petsmart. Also I know Beyond Spoiled which is Kathyrn V's website who is a member on here she also sells it. Missing Link is widely used on this forum too by many members it improves coat and skin quality....however it does take a month or two to see results.
Cowboy Magic is good for the coat to which you can search that as well so a lot of good information.
Nutro Natural CHoice is a good food I am surprised that it has made her skin worse. Its a good food for skin and coat as well. Have u had her tested for allergies??? That might help.
Does she need her hair shaved in the corner of her eyes...sometimes it gets long and it gets in their eyes and causes tearing...maybe someone will have a suggestion for that