Periodontal disease in yorkies can cause many issues. I do almost yearly dentals on my pups...of course it varies from one to the other. Some are worse than others. I have had pups who could actually benefit from dentals every 6 months.
It is hard to say if that is what is going on with her for sure...but since your vet did lab work and it is all pretty normal, he may be right that it is the cause .. You didn't say, but I am thinking maybe she hasn't had a dental in years. Brace yourself for the fact she may end up losing most or all of her teeth if that is the case....but, if they are bad, then better out of her mouth! I remember a little boy yorkie who was estimated to be 12 who came to me with horrible teeth...they were the worst I had ever seen. As soon as he woke up from the dental, he was a different pup! He was yapping and running around...it was funny. He was immediately better! Prior to that he was a quiet little thing...they must have been hurting him.
I hope the same result for Anna. With the antibiotic now and the anti inflammatory you will soon find out I think...just give it a few days.
Please keep us posted!