Molly Notkin spills everything — "That she’d said maybe it was…"
—That she’d said maybe it was her, she, the mother, who was the monster, which if so she was tired of hiding it and appearing falsely before God and man. —That whereupon she’d reeled from her place and hurdled three pointers and run down to the Daddy’s acid-lab in the cellar, to disfigure herself with acid.
Context
Joelle's mother, her denial-system blown at the Thanksgiving table, reaches for deformity as truth-telling: if she is a monster she is "tired of hiding it and appearing falsely" — self-disfigurement as the honest face. It's the U.H.I.D. doctrine run backwards (the deformed hide openly; she would deform openly what hiding falsified), and it puts the acid in the air of the story before the throw.