My sister does this in the flesh, @Bluntness100. She once asked me what had made me finally decide to have a child when I’d been leaning towards not, and I said it was partly something thought-provoking said by one of my best friends at the right psychological moment.
Cue my sister breaking out into an aggressive fury about how blatantly interfering my friend had been, she’d have told her to fuck herself, smug parents unable to understand people wanting to be childfree etc etc.
All poured out in this stream of invective, even though I had not actually told her what my friend said (it wasn’t at all intrusive), my sister has never met my friend (they live in different countries), I was clear to my sister that I’d appreciated it, and this had all happened nearly a decade earlier!
It makes her incredibly difficult to be around at times, and it’s lost her friends — this sort of borrowed aggression about something that’s not at all to do with her, and that no one else is asking her to condemn...