But if you've seen someone die and keep coming at you, trying to eat you, you could call them a monster even if there wasn't zombie lore in your world.

She's freakishly calm, and doesn't have the sense of anyone who's prepared for a hurricane or earthquake. She has no communication skills and zero sense of urgency.

They're all completely unable to communicate. Dad could have simply texted, "Emergency, answer your phone" and he could have told his Ex, when she was going on about visitation that it was an emergency. Both parents are lacking any parental, "I mean business" voices and meaningful looks.