You need to consider that not every 12 year old looks like a little kid. Some are very developed. I looked older at 12, and when my nephew was on a bus at age 13, he was asked by almost everyone who sat next to him if he was on his way to join the Army, or going back to college- he looked 18, and this kid may have too. So, if the calendar says he's 18, that's okay, but if he only looks 18, but is 12, that's sick? If he looked like a little kid, it would be, but I'm betting he didn't.
Still, even if he had been 18, it's still not cool for a married teacher to fool around with a student. But I do not consider her a pedophile, especially since he 'wanted it.' Remember the "Hot for Teacher" video? Adolescent boys dream of 'doing' the hot teacher, and if one gets her, he's more "way to go, dude!" than a suffering rape victim, like if a little girl were raped by force by a teacher.
What's the difference between her and Michael Jackson? First, he seems to get off on playing with little boys, many little boys, and they are bribed and scared into participating. She only wanted that one boy, the way she'd have wanted a man, for a mate. But bottom line is, they are happy now, and legal, so it's not for us to judge.