I'm of the opinion that Sayaka's not an angel.
As far as the discussion a few pages back about witchbombing girls, I'm with DK. It's a safety issue. Sure, some might have a more delayed reaction to the information, but with appropriate safety measures to prevent Tetris from happening, the impact from such events should be relatively low compared to an outbreak of Witchbombings. A Witchbombing outbreak would result in multiple deaths via witchout before we even noticed something wrong, and probably more as we rush to solve the situation. Whereas if we take precautions to witchbomb girls in small groups, some short amount of time after they've arrived (to give them a chance to settle in), we should be able to prevent them from witching and react immediately to any Tetris situations that arise. The major risks would be Tetris in that case, if we're personally involved, because we can prevent a group of girls from witching out via constant cleansing.
I do think there should be a slight delay to allow the girls to settle into the area. As such we should probably develop some manner of "pre-bombing" them, warning them that they're going to be in a high-density situation with girls of a mixture of different levels of information, and that there are infohazards present that could be highly lethal. And there shouldn't be any need to separate girls from girls - having witchbombed girls present during witchbombings and lichbombed girls present during lichbombings would be beneficial because they would have already developed coping mechanisms for such things.
I imagine eventually we'll have the manpower to set up the "classes" in such a manner that we don't need to be present to prevent Tetris. I could see them staffed by a teacher/psychiatrist and a small contigent of Police, all equipped with non-lethal techniques and Clear Seeds to prevent Tetris and Witchouts with the highest possible efficiency.
I think this is the safest way to operate a dense Meguca society. If we don't make absolutely sure everyone is bombed, and do it very carefully to prevent negative effects, then we put ourselves at risk of Infoplague, which could result in serious negative effects. There's a reason Pestilence is a horserider of the apocalypse - disease, even if it's a Infodisease, kills young civilizations. Not making sure our population is properly Infobombed would be like a modern society not making sure their sewers work properly, or not having hospitals where people wash their hands.