" She is not keen to do that, but I think that the reason is that she knows, deep down, that there were red flags early on, and that she ignored them because she was willing to ignore almost ANYTHING for someone of similar LOG/cognitive ability who (seemingly?) had so much in common and wanted a close friendship."

In today's life lesson, we learn that it's important to not ignore red flags because people give off vibes for a reason.

She shouldn't feel bad about ignoring the red flags, but she should feel bad if she ignore red flags in the future having learned this particular lesson.

" What we can't seem to do is get something on the record about HIM being a budding serial abuser, or keep him away from other vulnerable kids. My DD and I both are just SICK that he's going to do this to other girls. I realize that must be secondary to my daughter's self-interest, but she and I both struggle with that being "selfish.""

There's a way to deal with this, but I'm not sure what it is. In any event, high school is generally not a place to start a good record because it's prior to adulthood.

If you really want to solve the problem, just put a mental tracker on him and deal with him over time. This would be the Javert approach.

http://en.wikipedia.org/wiki/Javert

Dealing with problems like this is always difficult, but I wouldn't waste too much time on dealing with him at the moment. Plenty of time for that later.