When Elizabeth and the Gardiners arrive at Longbourn, they eventually go up to Mrs Bennet's room to talk to her. Mr Gardiner talks very sensibly to his sister, though it doesn't do much good. I imagine that he has had a great deal of experience with Mrs Bennet's fright, tremblings, flutterings, and spasms -- I suspect that she acted that way as a child even.
I really liked the way P&P2 presented this scene: the Gardiners & Mrs Bennet were pretty much spot on here, and it's one of Mrs Bennet's funniest bits (though sad, too).