To state the obvious. She remembered Jon crediting Farley for saving her life (or in your view, blaming her for killing Farley) and now Farley is dead and she connected the dots.
What sacrifice? You are mixed up. John said that to April, which was nothing but the truth, before Farley Died. He wasn’t blaming her for her death, because he hadn’t died yet.
I like that the Mom paid attention to Calvin’s panic amid her own distress. Also taking him seriously even though it’s just a stuffed toy (to her).