my cat gets sick and throws up a lot, she is 9 years old good health, plump not fat. seems to not to digest?

I'd have a vet take a look. Could be hairball problem, allergic to the food, dyes in the food (if feeding the cheap stuff like Meow Mix). Are you feeding dry or canned?

First off, quit changing her food around. If you suddenly change a cat's food without crossing them over slowly, it can make them sick. At her age, I hope you're feeding her a senior cat formulation, preferably grain free.

Second, if your cat was in good health she wouldn't be throwing up a lot.

Third, plump is still fat for a cat and unhealthy.

You need to take her to the vet for a check up. They will get her all sorted out.

First off, I'd have the vet check her thoroughly to rule out any medical causes. Then I would switch her to a high quality organic dry cat chow, available at feed stores, Petco, or Petsmart.

Have your Vet check her out. That's First!! Put her on Senior cat foods. If she gulps her food down, give it to her in smaller amounts a few times a day. But, first, have your Vet check her, especially at her age.

Have the vet check her out... It sounds like she could have a hairball, but to rule out anything serious, a trip to the vet is needed!!!