Malia cut right to the point. The bluntness took Libby aback. She wasn't used to straight shooters when it came to working with teenagers. Most teens she's met with in the past liked to skirt around the issue, whether it's denying that anything bothered them or simply attempted to distract her by getting off topic. The blonde managed to school her expression to keep her surprise mostly under wraps. The only tell that gave her away was a slightly widening of her eyes.
She blinked owlishly and said mildly, "Well, it's the rules of conduct in the classroom. Some might consider it a matter of good etiquette. Being respectful of the teacher's time by not walking out when they're in the middle of giving a lesson." Libby gave a little dip of her head to either side as if considering this but maybe not buying it as the go-to answer. "I think, more importantly, it can be a matter of safety. In the case of a fire drill or a real fire or some other kind of emergency, the school is accountable for the whereabouts of all its students. Was it necessary for you to leave right then?" Her question was genuine, not a reproachful demand and her continued light tone and relaxed expression made that clear. "Exceptions can sometimes be made for extenuating circumstances, like health reasons, if you're not able to hold off and wait for permission. But of course, that requires medical documentation."
She wasn't sure why Malia had trouble following the rules, but she had the impression that it wasn't out of a desire to be a troublemaker. As such, Libby was willing to explore the logic of the rules with her.