My advice to my favorite young relative is to understand the options. I might ask, "would you rather be with a smaller number of friends who have reasonable doubts and healthy skepticism and are prepared to change their minds when faced with contradictory evidence, or with a larger number of friends that are absolutely certain about everything?" I would also urge her to read up on organizations (not necessarily the ones she is considering) that have been classified by the mainstream as "cults", and see if anything sounds familiar or if any of it bothers her. Young people often have a rebellious streak and penchant for questioning authority, which can drive them either towards or away from such organizations. In the end, I want her to make an informed choice.