When the daughter created lie after lie and states the child is with a nonexistent nanny and does not show any concern about the whereabouts, you know who definitely is involved. There is no other possible explanation. She should be guilty of manslaughter at the minimum. In the multiple video and audio evidence it is clear that two of the three showed concern about the whereabouts of the child.
But Manslaughter was not on the table. Only aggravated manslaughter.