An essay I read before mentioned a word, conscience on the pillow. The general idea is that when you wake up suddenly at night, many things that have been ignored and suppressed during the day are also awakened, so that people can look at their own lives in the most objective and true way. There's a moment of regret or sadness, but then it's business as usual again when the day comes.
The timeline is probably one night in the summer before the Half-Blood Prince. After Bellatrix killed Sirius, if she discovered the sense of CP... The author doesn't know what happened.
The characters and world belong to Rowling.
Conception: