| Quote #1
They were of course very anxious to see a person on whom so much of their comfort at Barton must depend; and the elegance of her appearance was favourable to their wishes. Lady Middleton was not more than six or seven and twenty; her face was handsome, her figure tall and striking, and her address graceful. Her manners had all the elegance which her husband's wanted. But they would have been improved by some share of his frankness and warmth; and her visit was long enough to detract something from their first admiration, by shewing that though perfectly well-bred, she was reserved, cold, and had nothing to say for herself beyond the most common-place inquiry or remark. (6.8)
Lady Middleton is the most proper, "elegant" figure of a society lady that we see – and she's thoroughly dull. If this is being a lady is all about, we're not interested… and neither is Austen.
| Quote #2
Mrs. Jennings, Lady Middleton's mother, was a good-humoured, merry, fat, elderly woman, who talked a great deal, seemed very happy, and rather vulgar. She was full of jokes and laughter, and before dinner was over had said many witty things on the subject of lovers and husbands; hoped they had not left their hearts behind them in Sussex, and pretended to see them blush whether they did or not. Marianne was vexed at it for her sister's sake, and turned her eyes towards Elinor, to see how she bore these attacks, with an earnestness which gave Elinor far more pain than could arise from such common-place raillery as Mrs. Jennings's. (7.5)
Neither of the involved parties are being very ladylike here – while Mrs. Jennings is certainly not an elegant, prim and proper lady like her daughter Lady Middleton, Marianne also puts in her fair share of unladylike rudeness in her offense at the latter.
| Quote #3
"Elinor," cried Marianne, "is this fair? is this just? are my ideas so scanty? But I see what you mean. I have been too much at my ease, too happy, too frank. I have erred against every common-place notion of decorum! I have been open and sincere where I ought to have been reserved, spiritless, dull, and deceitful. Had I talked only of the weather and the roads, and had I spoken only once in ten minutes, this reproach would have been spared." (10.5)
Again, we see Marianne struggling with notions of what a proper lady does. While she can recognize crimes against convention in others (such as Mrs. Jennings), she always hotly defends her own conduct when it's outside the realm of the ordinary or proper.