You did everything you could have done, anything else would have fallen on deaf ears. Hopefully she will take your advice about joining Yorkie Talk, and she will learn something.
Aside from what you pointed out about the dog being a "teacup" and only 9 weeks old, I can't believe they had a puppy in a public place like that, where lots of dogs come and go, well before the pup had all of it's vaccinations. Are they ever asking for trouble, at the pup's expense.
