I think it is wonderful you are doing what you can to help your yorkie baby,
Just be sure she is eating , and when you get to the vets in January bring up your concerns again about her loosing and gaining so much weight .
I 'm pretty shocked at how quickly adults are to jump do the throat of a well meaning obviously loving teenager , who just wants help .
I do want to say in all of the teenagers post she was in my opinoin respectful , even when some of the so called helpful answers to her question were out right mean.
Good luck to you and your baby , monitor her weight and until you are able to get her checked out , do make sure she is getting proper nutrition.