Give her a light bath with Dawn dish detergent. Yes it works. I believe you leave it on for a few minutes. Make sure you completely dry the puppy, she is so little. Even if it means use a blow dryer, on low heat.
You probably did not know this but little Yorkies are not suppose to leave their Mom and littermates until they are 12 weeks old. The are not like the bigger breed dogs. So I'm surprised a Yorkie breeder didn't know this. You could have a lot of problems because she left so young. But we will do what we can to help you.
Now you could easily experience what is known as hypoglycemia. VERY DANGEROUS and it affects this breed easily. If left untreated,they will die. Their sugar drops and starts to close down the organs. Did the breeder discuss this with you? What causes this? Them not eating or even skipping one meal. Being stressed fromeaving Mom and being in a new place. The little one, because of the age needs to be fed often, at least 4 times a day. Stress. If she seems to want to sleep a lot, it's ok for pups to sleep but if need be, wake him up for him to eat. If he doesn't seem to want to wake up, or you see him walking funny, like he is drunk, you need to give him nuti-cal immediately. If you don't have it then Karo syrup. You must get the sugar level back up. I would even put a little in his drinking water anyway as a preventitive.
Who is the breeder anyway? Does she live close to you?
Here is some info. Please read because these pups can't afford fleas sucking what little blood they have. Good luck and keep us updated and post if you need help with anything, ok?
Toy Breed Hypoglycemia