[smartpuppiepets]

Wow... big story ... not fun !
Well, first of all, a breeder letting small puppies go home to young, either inexperienced or doubtful responsibility.
Parasites such as Giardia and or coccidia could explain all the symptoms you are experiencing and the fact that she went to you way too young. Not every puppy will stress out to the point of having these parasites overgrow and show those symptoms, so the fact that the siblings did not show any stress signs is not a good reference.
The other breeder gave you great advice as far as the feeding. Not feeding is definitely not an option, she needs to be fed round the clock every 2 hours and the "a/d" food is a great choice. You liquefy it and syringe feed it . Honey is not the best option, nor it is sugar. the more you give, the unstable she will be. Do you know anything at all about insulin levels in the blood and how it is better to get it stable rather than having "peaks" of it , that eventually will cause diabetes?
The thing with smaller yorkie puppies is this: Once the insane cycle of stress and sugar lows is started it is hard to stabilize it. But not impossible.
You need to offer 3 things basically:
1 - energy stability ( sugar stability) by feeding her on a schedule a very good quality food. For now a/d will do fine and as she stabilizes she will show more and more interest on the dry kibble of your choice.
2- You need to free her from the parasites. 5 days of meds probably did not do the trick. "Albon" combined with "Flagyl" for 9 days and "Panacur-C", These 3 meds for the 9 days is what you need to give. Of course you must get these from your vet and i am surprised they have not done this protocol yet.
3- She needs routine and rest. Plenty of rest. 20 mins of play and attention followed by 40 min of rest. She can not handle too much noise, new environment and different people handling her. She needs a quiet routine until she gets that adrenaline rush under a controlled balance and slowly get introduced to different things, new people and all.

From what you describe, this is a tiny yorkie puppy under a whole lot of stress. The fact that she seems happy and it is like a fireball sometimes just confirm this. Too many distractions, too much activities.

Hope i gave you some insights.
Blessings.
XOXO