My edition of S&S has an introduction which discusses the dangers of letting young women indulge their 'sensibility' too much. The author of the intro (sorry! book is packed for a move and I can't remember her name--perhaps Margaret Anne Doody?) says that we can look at how Lady Middleton taught her little Annamaria to pitch a fit to get her way, describes Marianne's (Annamaria flipped) danger in taking her 'romantic sensibilities' into a harsh world, as well as other 'ruined' emotional characters like Eliza I and II. But the book also shows how women in that society were expected to faint, be more 'sensible,' etc. and it was considered a positive feminine trait to a certain degree--women are quick to feel, etc. It's only when it gets out of hand and a young woman 'dies for love' or doesn't understand the real rules of courtship and marriage (the Elizas, Marianne) and gets in, or close to, trouble, that sensibility is 'too much.'

Fanny Dashwood, it seems, from your perceptive picking apart of her 'hysterics' and 'agonies'--thank you, Robbin!--knows how use emotion as a means to an end. If she can 'hysterically' demand that the Steeles be driven out, it's more feminine than coldly making them leave. Her angry, 'rational' demands are sandwiched between 'hysterics' which are probably, or largely 'fake.' Here's my take. She is angry because she's been deceived by Lucy and Edward, and maybe a little hurt. She fears her mother will blame her for having Lucy under her roof. She is frustrated because she have to deal with the situation: break off the engagement, along with her mother using their influence over Edward, and keep it all from Miss Morton and the rest of 'society.'

On the other hand, you could see Fanny's hysterics as real, because if she wanted to hush it all up, keep it from Miss Morton, and maybe pay off Lucy so she wouldn't cause trouble, she would have remained perfectly calm as she explained to Lucy that her mother would never give them any money, and that Lucy might be better off taking a payoff to go away quietly. She should have realized that the 'hysterics' story would get around town. Oddly enough, in this scenario it's Robert Ferrars, a male character, who plays the role of counselor to Lucy.

But how genuine are the hysterics of any woman, Austen seems to be asking? Are they all created by cultivating little Annamarias and Mariannes, (and maybe Mrs. Dashwoods) who prioritize emotion, or is 'sensibility' innate? Remember her early words "Run mad as often as you chuse; but do not faint?" Why do the Lady Middletons, Elinors, Fannies, Lucies, exhibit more 'sense.?' Innate or learned?

And I don't know where to put Mrs. Jennings, Mrs. Palmer, or Anne Steele on the 'sense' or 'sensibility' continuum.