A tip I read on Dear Ann or Abby, one of them, many years ago - she was advising a woman who had the same problem.

Or actually - I think another woman wrote in to the column with her advice.

Anyway - whenever she got berated or hassled by the MIL, she would say, "You're absolutely right. I don't know HOW you tolerate it."

Tended to stop the barrage right in its tracks.

Might work with ANY annoying person, actually!