Some yorkies do just have thinner coats than others. Being that she is 5-6 months old, it's possible she has lost her puppy coat now and what you're left with will be just a naturally thinner coated yorkie. You can try changing to a better quality food, adding supplements, experimenting with different shampoos, etc., but if she is one of those yorkies with thinner coats, it's not likely to increase substantially her amount of hair.
My Ruby has a fragile silk coat that is very thin, it breaks easily. I've tried numerous supplements, feed great quality food, use wonderful shampoo/conditioners and nothing seems to make much of a difference. I've resorted to using very small, lightweight bows for, when I really want her to wear a bow.
__________________  ~Ruby, Reno, Razz, & Jack~ |