Lyric discussion by zenwizard 

Cover art for Mary lyrics by Oingo Boingo

What makes you think she turns to prostitution?

I thought the song was about a girl who left the safety, comfort and ignorance of home and wanders off, like a nomad on a spiritual mission, a conquest of her soul. I think it is a spiritual journey, because of the words, "she left all her friends to wander all alone" (almost like a modern day Jesus) and "That mountain that she had been taught" (mountains are stereotypically places of gaining insight) and "she grew so much inside" (inside, meaning spiritually). Anyway, she returns home to free her parents and friends from their [religious] ignorance (they are probably conservative catholics), and finds she that they are incapable of understanding her revelations.