Has Jenna vomited up worms? If not and she has just been sick, then the sachets obviously don't agree with her. It's really a case of trial and error as to what her stomach will tolerate. If she kept the sachets down for a few hours then they should have had time to take effect so I wouldn't worry too much. If not, then you should get an alternative treatment if she is suspected of having worms. In future, I would probably use another product. Neither of my dogs are sick on their respective treatments but there have been many who phone the surgery to say that their pet has been sick with whatever worming treatment they have been given - switching products usually does the trick.