I don't understand why people have such a disdain for Mormons. I really feel like most people know next to nothing about Mormons and they get a totally unjustified bad rap. I have a Mormon friend who's family moved her to Utah to be even more Mormon, and every time I've asked her about something, she always said something along the lines of "I don't know where you heard that, but I wasn't ever taught that, and never knew anyone who believed anything like that." She also loves the Mormon episode of South Park.
You also don't learn about Xenu and body thetans until you're a couple ten grand into the scientology game, and by that point, you're too invested in it to throw away a major part of your life. See if she knows about the holy underwear.