4 ideas
In it she revisits her marriage, the social rules of her class and her distance from her gay son, whom she never accepted or understood. The confession comes only when she has nothing left to protect, which is why it can be honest.
A terminal diagnosis removes the social stakes that enforced a person's silence: reputation, marital peace and standing among peers stop mattering. The dying writer can finally say what the living self could not afford to say. The same truths stayed unspoken for decades because the cost of saying them fell on the speaker's future, and now there is no future to pay it.
A mother's failure to accept her gay son is not a private emotional flaw. It is how her Catholic, upper-class milieu enforces its norms, carried out through the person closest to the child. She rejects him partly because he threatens the conformity she herself submitted to, so admitting he is right would mean admitting what her own obedience cost her.
The narrator can only begin to understand her son once she examines her own repressed desires and her unequal marriage. Her attempt to understand the child turns into a reckoning with herself. The inability to see another person often protects a truth about one's own life, so understanding them requires facing that truth first.