The mother did not torture the LW by regaling her with tales of her father's infidelity. She mentioned it once, after a giant fight with her cheating husband, and regretted it pretty much immediately. Asking the 10 year old to keep it a secret was a big mistake, but people do all sorts of strange things when they are ashamed of themselves.

The LW has brought up what was undoubtedly a very unpleasant subject to the mother over and over again. Remember, Mom was the one who got cheated on! No wonder she does not want to discuss it at length with someone who never should have known in the first place.

What kind of contrition would be good enough for you? Obviously, working to fix the marriage and ensuring it never happened again doesn't count. Neither does never again burdening the child with painful information like that. You say an apology would also be inadequate. Should she pay reparations? Cut off a pinky finger? Grovel on her belly?

Some people are behaving like this mother was burning her 10 year old daughter with cigarettes or something. It was a stupid, one time mistake!

Lucky for the LW her parents didn't get divorced. She is so emotionally fragile that she would probably be living in a crack house by now.

Freki