This isn't quite fair - it's not so much that it's horrible to say, but that it's easy to say when you aren't emotionally invested in the relationship. Nobody would criticize someone who jumped ship if this episode happened on a first okcupid date. There's a reason this subject didn't come up in their conversation for eight months, and I don't blame her for that.

On the other hand, I know a guy who was about to break up with girl when she got a cancer diagnosis. He stayed with her for years, miserable, because he didn't want to be that schmuck.

Relationships are complex. It's poor form to criticize someone who stays, but also poor form to criticize someone who leaves - there's a lot more going on than just one issue, even if it is a big one.