Welcome to YT! How nice that you have adopted an older yorkie!
Does she have hair on her ears? Sometimes they can get what is referred to as leather ear where they have a black build up on their ears and the hair falls out. It can sometimes also extend to the nose and legs.
Check out these posts and see if this is what you are experiencing.
http://www.yorkietalk.com/forums/sea...archid=1736436