A parasite harms the host with no benefit in return, like a Tapeworm or tick. A symbiote creates a mutually beneficial situation, like bacteria in our gut that helps digest food. So yes, she is correct that we do need certain critters in us to be healthy, but not "parasites". The critters you are trying to get rid of by doing a parasite cleanse are true parasites. Typically after doing a parasite cleanse you would even attempt to reintroduce symbiotes to your body that were killed off by the cleanse, like the good bacteria in your gut. Probiotics are a good example.