Like endthematrix said, your sister is referring to The Davinci Code by Dan Brown. As the background premise for his mystery, Brown takes some interesting historical oddities and weaves a mythological version of Christianity where Christ married and early priests conspired to wipe-out all traces of this from the record. Basically, the novel claims Mary Magdelene was "whored up" by men who did not want to acknowledge her special role in their religion. The reason they would go to such lengths to do this is chalked up to the desire for power and generally to keep women down. The theology in the book, which is a fast-paced cryptological murder mystery, is a mix of Christianity and goddess worship. The bad guys are Opus Dei, what you might call a fundamentalist catholic sect. As such, they were a safe smear target which, along with its generally sacrilegious rendition of Christianity, ensured the book would be lauded by reviewers (Mel Gibson has been criticized for having informal relations with Opus Dei, if that gives you any indication). Brown took more than a few liberties with historical facts, to put it mildly. But it is true that if you look at the Last Supper, the person seated next to Christ in the painting is certainly a woman upon close inspection, and long before the book was published I had read theories that Christ married and fathered children who began the various royal lines of Europe (which--even though I don't believe it is true--would explain how the royal families developed and why there was such a persistent belief passed down through the ages that they were chosen by God). As a piece of fiction, The Davinci Code is a bit shallow and gimmicky, but a fun, if silly, read. As a historical account, it's a just piece of fiction.
Do you have some thing against paragraphs?