I would only use something from the vet's especially on a kitten. I got two different kinds from the vet's for one of my kittens, one for roundworms and he was a rescue that had been badly infested with fleas so she went ahead and gave him one for tapeworms. It really wasn't that expensive, much safer, and you know you're getting something that will work.
OTC wormers can be dangerous and often inappropriate, especially for a kitten. The vet needs to determine what kind of worms she has and will work out the dosage according to her weight.