In an FAQ on that site, LaMorte writes that while she was once a proponent of New Age beliefs, she rejected them after her conversion to Christianity.
While the Scoobies are busy preparing for the parents, Giles (Anthony Stewart Head) and Jenny Calendar (Robia LaMorte) show up to inform Buffy that Saturday will be the Night of Saint Vigeous, named after the leader of a vampire crusade, and that during that night, the natural abilities of vampires will be enhanced.