First of it's sad and disgraceful what this girl has been through, but ice read some posts of both threads and If we accept casual sex is ok (has been the mantra of feminism I believe for a long time to dispel the women as sluts thing and it takes two to tango) I don't see what else this guy could have done if she did indeed look older, was out at a time you would reasonably believe an underage girl to be out etc.
I've seen posts about women carrying cards to say they're of legal age to have sex essentially, well isn't that just ID that could be faked? So it wouldn't be anymore helpful, and it will then just spread the notion that women can't be trusted, what else should women not be believed on that they're on birth control? Maybe have a paternity test as part of pregnancy?
This is a whole fucked up situation with sadly not many solutions