Behold Elinor Dashwood, Queen of Double Meanings!
I love the conversation between Elinor and Lucy. Elinor never says an untruthful word; instead, she speaks in double entendres (but not of the naughty kind). E.g., In response to Lucy's assertion that she believe Elinor had been offended during their last conversation, Elinor says this: '"Believe me," and Elinor spoke it with the truest sincerity, "nothing could be farther from my intention than to give you such an idea."' In fact, Elinor was upset/offended by their last conversation, but her goal in this conversation is to smooth that over so that Lucy won't suspect her of being dismayed. Note that she doesn't say she wasn't offended, just that she doesn't want Lucy to think she was offended. Clever, clever Elinor (or, if you prefer, clever, clever Austen).
Austen makes sure that we see Lucy's uneducated mind at work, in part through the use of irregular verb tenses. Lucy's lack of polish is clearly evident in sentences such as this one: 'I felt sure that you was angry with me; and have been quarrelling with myself ever since, for having took such a liberty as to trouble you with my affairs.' (In my mind, this sentence calls to mind Jean Hagen's performance as Lina Lamont in Singin' in the Rain, who says "If we bring a little joy into your humdrum lives, it makes us feel as though our hard work ain't been in vain for nothin'." God, I love her lines - and Hagen's performance! But I digress, even though both Lucy Steele and Lina Lamont are manipulative women who are beautiful, but crass.)
Elinor susses out Lucy's true feelings for Edward, which are, essentially, disregard of him as a person and deep interest in his income. Elinor feels especially sad for Edward, because "he had not even the chance of being tolerably happy in marriage, which sincere affection on her side would have given". And Lucy can no longer be certain that Elinor loves Edward, but she continues to suspect her of doing so.
We learn that Lucy continues to rub her engagement to Edward in Elinor's face at every turn, that Elinor shuts Lucy down ASAP when she brings it up, and that the Steele sisters hang around through Christmas ("that festival which requires a more than ordinary share of private balls and large dinners to proclaim its importance").