Though I haven finished the story yet, it appears to me that Maggie suffers severely from PTSD and my theory is it has developed her wizard's sight, thus she sees the young bullies like versions of vamps.. In truth their instinct to attack a perceived weak a vulnerable child among them makes them that.. I think if Harry were to look at those kids with his sight, he'd see them as Maggie and Mouse do.. However as we know, unlike Maggie he has control over his sight. Now what Mouse sees lurking in the wings as the controlling entity might be something else. Haven't got that far yet but I think it might turn out to be Austin's monster from the Nevernever, perhaps one of the Ebs that escaped the slaughter at C.I. but in a new form. Given Austin's age in relation to Maggie's age, if he returns, possible future husband for her?