now a sex offender because when he was 18 he had sex with a girl he thought was also 18. Turned out she was 16, and despite his belief, and her saying she was 18, he was convicted.

Either facts like this can be mitigated by one being deceived, or it doesn't matter. I don't know what the law says. But if it does not allow for you being deceived, you are guilty, right?

I don't think there is much difference between someone who is 17 and half years old versus just turned 18. But perhaps there is between just turned 17 and 18.

I think what happened to this poor girl is she somehow became very interested in sex, maybe already having done it. Whatever it was obvious that night, she was looking for it, and looking for it a lot. And then the next day realized how horrible she felt, etc. Maybe saw the vids, or something and felt guilty. And that led her to shift the blame. Whatever happened, how horrible for her to make this choice.