Sometimes kittens get swollen "pot bellied" stomachs when they are infested with parasites such as tapeworms or roundworms. These parasites are extremely common. They are so common that it is recommended that all puppies and kittens are dewormed several times during their initial vet exams. If Sam hasn't been dewormed I would suggest taking her to the vet and getting a stool sample checked as well as deworming medication. There are more serious problems that could be going on, but hopefully this is just a case of parasites. Good luck with Sam! Feel free to reply with any other questions.