Late to this party in your series of questions : )
Combining the three posts that I have read, I am going to suggest that you start with consideration of her diet. Sounds like it might need to be redesigned. Chat with your vet, ask about a basic blood panel, see if you can find out what her deficiency or overload is and where it is coming from, or if it IS a deficiency or metabolic issue.
Dry feet, skin, mouth, just about anything dry on a body is a common sign of deficiency.
Be aware that if you DO modify her diet, it can take up to a couple months to show the beginnings of any change or improvement. Diet related issues often take forever to present any clear sign/symptom (hard to remember that a lameness or twitch or some odd reaction can be diet-related) and the recovery can be just as slow.
Re-evaluate her diet.
Patience : )
Sure there's right and wrong but mostly there's just a whole lotta different.