I've learned that sometimes parasites don't show up in a single fecal test...or a second...
It could be giardia which my vet said is the parasite that can go undetected.
Take her to the vet right away - my Maggie gets sick but acts perfectly fine. She didn't have a good reaction to her distemper vaccination - vomitted for 2 days - with the next vaccination, the vet gave her benedryl before the shot and it worked
beautifully!
Keep us posted!