I'm surprised to haven't seen this mentioned yet, but based on the article and skimming the emails linked to, the woman was very religious, and the guy not at all (but went along with it anyway).
I'd argue that if you're an atheistic person, then the worst case scenario of dating a very religious person is something like that story. The amount of cognitive dissonance and self-imposed guilt and shame in religious people, especially when they're still young, is very likely to lead to messy situations like the one described. Young people are full of hormones and impulses that they want to act on, but the religion in their head tells them to feel bad about it. This can lead to absolutely absurd situations, where they're very happy to have sexual relationships but feel very guilty after them.
I dated a religious girl, and the emails exchanged by those 2 reminded me of my own relationship 7 or so years ago. Fortunately my story wasn't as messy as this one, but there were definitely a couple of hard earned lessons and very uncomfortable moments. Some of the stories that girl told me about her earlier life were quite unreal to me- for example, she and her ex boyfriend would have sex, then she'd feel guilty and go confess at church, and a day later they'd have sex again, etc. (if you're a priests, you must get to hear a lot of intimate stories from impressionable confused young people. And of course all priests are men... connect the dots as you will)
It's hard to draw any conclusions based on the article and material available - but to people that have found themselves in similar relationships, some of the interactions described aren't surprising. The lesson for me was, date people with world views similar to yours.