]I find *some* similarity between LM and Elinor.

At first I found this idea rather shocking but upon reflection perhaps Lady Middleton is a failed “Elinor” and that is why she seems very, very superficially like her--they both do present a calm, composed exterior to the world but what lies underneath is quite different IMO. LM’s good breeding is not augmented by taste and talent or an affectionate disposition and I think it is certain she does not exert herself on behalf of others as Elinor does. A direct comparison of Elinor and LM as described by the narrator shows them to be completely different kind of women. Where Elinor has an excellent heart, affectionate disposition, and strong feelings LM is reserved, cold, and insipid:

Elinor, this eldest daughter whose advice was so effectual, possessed a strength of understanding, and coolness of judgment...She had an excellent heart; her disposition was affectionate, and her feelings were strong: but she knew how to govern them… (Chapter 1)

Lady Middleton…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…though perfectly well-bred, she was reserved, cold, and had nothing to say for herself beyond the most common-place inquiry or remark. (Chapter 6)…but the cold insipidity of Lady Middleton was so particularly repulsive…(Chapter 7)

From Chapter 1, Elinor exerts herself on behalf of others in social situations which are different than LM’s sitting around and not saying much. At Norland, Elinor carries the burden of attending John and Fanny alone because her mother and sister would not. As well as her attention to Col Brandon—off the top of my head—Elinor engages in the defense of Col Brandon to Willoughby and is even declared to be “saucy” by him in Chapter 10—could not get much further from cold and she participated in LM’s favorite subject (her children) in Chapter 6 which is more than LM is willing (or perhaps capable) to do for anyone—participate in conversation of their favorite subject. I can think of two instances in the text that shed light on LM when she is apart from company. We know that at home her husband finds her often unemployed (Chapter 9) and in Chapter 11, LM is described by Elinor as treating her husband and mother in the same reserved manner she treats the Dashwood ladies—I think this prohibits any warm-hearted discussion at home. In Chapter 6 the narrator says LM is reserved and cold with nothing to say for herself beyond the most common-place inquiry—(lack of resources, intellect) and in Chapter 7 the narrator refers to her cold insipidity in relation to how she treats other people. This is two specific descriptions by the narrator of LM’s demeanor which to me give a very clear picture of a woman with only a little more animation than a cow—I can almost hear the cud being chewed. A few chapters later Elinor observes the same thing:

Elinor needed little observation to perceive that her reserve was a mere calmness of manner with which sense had nothing to do. Towards her husband and mother she was the same as to them; and intimacy was therefore neither to be looked for nor desired. She had nothing to say one day that she had not said the day before. Her insipidity was invariable, for even her spirits were always the same… (Chapter 11)

The description of “cold” is not used with regards to Elinor and LM in the same way, also the authority which uses it is reliable on one hand and unreliable on the other. The word cold is used by the narrator to describe a LM’s reserved manner to all the world but her children; Marianne’s extravagant sensibilities are offended and she calls Elinor cold in relation to how Elinor expresses her feelings for Edward in Chapter 4, this is not a reflection on her sister’s general temper; it is a comparison to Marianne’s over the top sensibilities—how she would act in the same situation. I believe Marianne finds everyone but her mother and Willoughby cold in their expressions of love. In Chapter 8 Marianne says that Elinor’s and Edward last adieus are cold and she equates cold with composed. Again Marianne is disparaging Elinor’s and in this case Edward’s expression of their feelings in comparison to how she would act and once again it is not a reflection on their general tempers. Lastly, I do not think Marianne is a good judge of what is a cold manner, her judgments are always suspect because her standards are over-the-top in their sensibilities—surely you do not agree that upon leaving Edward, Elinor should have been dejected and melancholy, avoid society, or appear restless and dissatisfied with it as Marianne suggests in Chapter 8. The narrator however, I do believe to be a source of true and useful information on this subject unlike Marianne. :D

IMO Lady Middleton does not advise her mother, she scolds (Chapter 13) or draws attention away from her mother (Chapter 12) and it is not for the benefit of her mother—it is predictably concerned with maintaining decorum—I am not saying LM is wrong to “save decorum” but scolding and being embarrassed by your mother so much you wish to draw attention from her is not the same as giving advice. What sort of evidence from the text do you have that LM advised her mother before her marriage and if she did it was spectacularly ineffective because Mrs. Jennings is exactly the opposite in manner than LM. Elinor, however, is in fact an advisor to her mother-advising her to sell the carriage and not to rent houses too expensive for her income and on the lack of need for a new grate in the guest bedroom. In addition the narrator tells us in Chapter 1 that Elinor was qualified by disposition and temper to be an advisor to her mother and that her advice was effectual.