Awwwww...poor little girl. Her skin and hair look really dry. My first guess would be allergies or maybe just plain ole' dry skin. What kind of food are you feeding her? A lot of yorkies are allergic to corn, which is in a whole lot of dog foods. Maybe you could try switching her food to something like Chicken Soup for the Dog Lover's Soul or Merricks. My parents' yorkie is 7 and her skin and coat don't look like this. This is what makes me think it isn't old age and it is something else.
P.S. -- Welcome to YorkieTalk, fellow Alabamian!