Obanta seems to use SARAH's surveillance ability far more invasively than other UNJE officials (or at least is way more obvious about it). It seems fairly clear that Anika's and Ryan's argument was observed, for instance. She'll find out about Karen very soon (possibly immediately, given the weird hookup thing she has in her office). Mentalists cheating is harder to detect, but people acting on or speaking of info they aren't supposed to have could still be detected.
It doesn't seem unreasonable to assume that much of the point of mentioning classified info and asking people to leave the room is to see how that info spreads around. Just as the teens might want to meet and sound out their new boss, she might want to find out more about how the students react. Or perhaps give them enough rope to hang themselves.