Sounds like she might and a urinary tract infection. You should really take her back to the vet or at least call them and ask them. If she had worms, round worms are more common in kittens. There would be small white and coming out her anus, she'd also have a pot belly. If that's the case, then you need to get her to the vet, change the litter box frequently and follow the vets course of action.
My 8 month old kitten has worms. This is the second time she has had them. She started out sleeping more than usual, and I noticed that she didn't seem to be putting on much weight. I knew something was seriously wrong with her when she vomited and had diarrhea, at the exact same time. She was also bleeding from the rectum. When I cleaned up the vomit, I could also see white stringy things in it. If you take a stool sample to the vet, they can do a fecal test quickly, which will confirm whether or not worms are present. If your kitten does have worms, the vet will give you some medication which you'll give her in two doses. After about two weeks, you'll have to take in another stool sample to be tested to make sure the worms are gone.
