Dog poisoning?

Question
My yorkshire terrier has been under the weather for about a week, coming on two now. At first we thought it was a psychological thing, she seemed depressed, was losing interest in her food, seemed nervous and lathargic alot of the time and was lying down in strange places. (under furniture/in the corner)
However now she has been sick around 4 times, we thought it was a stomache bug as my labrador was also sick at the same time, but she is better and the yorkies still ill. She has lost a fair bit of weight quickly, has slightly blood shot eyes and her mood is still off.
We took her to the vets and they said it was probably her teeth, so she is having them done tomorrow. However she has been eating some boiled chicken and on a few occasions has thrown it up shortly afterwards, that leads me to believe its not just her teeth.
We have some plants, mainly types of grass, around the pond and when she threw up the other day there was some plants in it. Shes also walking around in a hunched up manner occasionally which leads me to believe she has stomache pains and she is very frail.I believe shes poisoned herself and im very worried, what is your view please? Would appreciate a quick and logical answer from someone with expertise, not opinionated answers. Thankyou very much, Ed


Answer
Ed- Don't do the teeth tomorrow!!!!  Please don't... It would be very dangerous to put her under anesthesia.  What did they say was wrong with the teeth>>>>???  Did they look abscessed and need removal?  Was it just some tarter build up?

I have some suggestions but need more info?

Also, did they do any blood work on her?

Let me know...
Thanks