>>138120553They were probably hoping she would sleep through it and would wake up the next day and just assume they abandoned her, likely with Papa Sprite even telling her that's what happened, letting her sadly go home and only suspecting something when the other four never showed up to class again.
It's still a stupid plan. At some point Ellie is going to have to explain to the police why four teenagers she was last seen with have gone missing. The best case scenario for them is that she can never prove the Sprites exist, and Ellie is put in a straight jacket for killing her classmates. The worst case scenario for the Sprites is that this adds up with other disappearances in the area including ones that happen AFTER Ellie was arrested or when she's too young to have done it herself, and authorities show up to destroy the land and genocide the Sprites.