If I see yellow vomit, I would treat for low blood sugar 1st, especially if she is quieter than usual. I use Nutri-Cal for raising the sugar level, available at your Vet. If it goes low, before you get some, a teaspoon of Karo syrup will help.
When you register you pup with AKC, they send a certificate for a free Vet check, I think.. I don't know if you have to actually get the insurance or not. I don't use insurance, and I haven't paid much attention to the paperwork about insurance. But some of my puppy buyers have mentioned the free Vet check.
There are many reasons for bile vomit.. so as much as it hurts, she needs a Vet check. Losing interest in food previously liked is a red flag to me. She needs blood work. Does she have diarhea? A stool check for worms, and cocci would be wise too. Maybe you could find a Vet that accepts monthly payments. I hate to be the bearer of bad news, but Yorkies are high maintenance, and you "ain't seen nothing yet"...
Good luck, and let us know how she does at the Vet.