Is she eating much durring the day? And is she eating her regular food while she is with your mom? If Maddie eats another dogs food, even a little bit, it can make her tummy upset.
They also can get low blood sugar if the go too long between meals, this can cause them to throw up, become lethargic, unresponsive, it can also cause siezures, coma, or death. Yorkies are prone to hypoglycemia (low blood sugar) especailly if they are on the smaller side, or dealing with other health issues. She should be eating small frequent meals or be free fed if possible. If you think that it might be low blood sugar I would pick up some nutrical and make sure she is eating more often.
I hope that you find out what is going on with her soon. And that she starts feeling better.
