If asked, Mary would say that she wants to hear the truth. That it is better to know than not.

All the same, she doesn't want to hear this. She stares sullenly at her knees, as she demands, "Why?"

Her parents are in Heaven. She expects it's nice enough for them. But Lucy isn't like her parents - she's here, and she seems more alive than her parents ever did. And Mary does not think, in any case, that they would get along.