My sister married a man from outside the group years ago, she ran away from home in order to do it as she was still just 19, but in love. Unfortunately the love blinded them both to practicalities. He was a really clever man so perhaps he thought he could guide her out of the cult, it should be easy right? It isn't just difficult its near impossible for an outsider to deprogram a cult member. Then there were the practicalities, she would't go to a Christmas dinner with him to his parents house, she wouldn't celebrate his birthday, valentines day, Easter, independents day, guy Fawkes, new years eve celebrations...the list goes on! Then they had a baby together. Can you imagine his frustrations as his child was being groomed by a cult? As he was becoming isolated in his classroom as he was so different to the other kids. Eventually after years of a troubled marriage they divorced. Years later he had to see his son decline a university education so that he could spend most of his time knocking on doors.
Update: what village says is true too! My sister left the religion for a short period when she got married, but this was due to the guilt of breaking a rule and marrying a 'worldly' person, she was not deprogrammed so in time she returned.
Good suggestion above though, what will her reaction to JWfacts website be like? Can she be deprogrammed or will her cult barriers go up, will she demonstrate that she is under information control by saying such things as 'I don't want to read this site! People lie about our religion!' You have to base your decision on her reactions.