Yorkshire terrier throwing up.

Question
My puppy threw up once today. she was sleeping and she was woken up by
our front door. she was still up and half asleep and she started to throw
up. Then i put her down on the floor and she went under my bed and threw
up again. the first time on the bed, it was a lot of throw up. usually it is
never that much. then she did it again on the floor but not as much. then
she fell right back to sleep after i took her outside. and again, she woke up
and she threw up again. it wasnt a lot like the first time. we feed her
natural balance and she doesnt eat too much. she does eat her own poo.
and she started to eat her throw up. this isnt the first time for her to throw
up. we took her to the vet and they said it was just a change of food. and
she has thrown up in the car about twice. the first time i wasnt there but it
was just yesterday when she threw up in her bag in the car. that smellled
like poo. but today it smelt like dog food. she has been sleeping for a while.
do you know what it can be?

Answer
It sounds like she isn't getting along with the food.
Changes in diet usually result in diarrhea, not vomiting. But a food that she is not tolerant of can make her vomit also.

Eating her own stool usually doesn't cause them to vomit either, but if she is eating the (recycled) food that isn't getting along with her stomach, then she will vomit from that also.

It sounds almost like she has gastritis. This is an inflammation of the stomach.
If she continues to vomit or starts to have diarrhea, then she needs to see the vet. She may be coming down with parvo virus also. You didn't mention her age or vaccination history so I don't know how protected he is.

Natural Balance is not the best diet in the world anyway, and she is obviously not happy with it. Once she is feeling better you should get her on a more consistent (in quality) diet such as Science Diet puppy growth.