How could she not have thought about letting him die? But if he really died, it wouldn't be fun at all.
When he was very, very small, still capable of crying, watching him cry was such a blissful thing. Unfortunately, this little creature was truly naturally stubborn. Gradually, he stopped crying and would look at her with a kind of resentful gaze. Whenever she saw that resentful gaze, she found it extremely amusing.
He hated her, but on what grounds did he hate her?
He would never know how much she hated him, so much that him dying a million times would not be enough to quell everything she lost because of him.
So she would never let him have it easy. She wanted to always watch him suffer, watch him live a life worse than death. Only then could her life, ruined by him, sense a tiniest bit of joy.
