I would not recommend buying any over the counter deworming medication as many of them are very dangerous for her. I would suggest bringing her in for her first checkup at the vet's and discussing a vaccination procedure that is best for your cat, and getting a deworming medication from him/her. Revolution is a good product to use.
De-worming should be done based on the results of a fecal test (at the vet's) so that only the parasites that the animal actually HAS are being targeted. Many kittens have roundworms, for instance, which a round of Strongid will clear up. You don't want to give drugs that might be unneeded and might be dangerous.