I definitely noticed that Lucy is the one in charge in the Steele sisters' relationship, and it is Lucy who is giving advice to her or smoothing over her social missteps, as Elinor does for Marianne.

Although Elinor would not like to be likened to Lucy, I found a lot of similarity among these exchanges:

(ch. 22)

"Norland is a prodigious beautiful place, is not it?" added Miss Steele.

"We have heard Sir John admire it excessively," said Lucy, who seemed to think some apology necessary for the freedom of her sister.

"How can you say so Anne?" cried Lucy, who generally made an amendment to all her sister's assertions.

and (Ch.23) Marianne informs Lady Middleton she detests playing cards and is going to play the pianoforte instead.

' "Marianne can never keep long from that instrument you know, ma'am," said Elinor, endeavouring to smooth away the offence;'

Of course, there's more going on with Lucy and Anne than just one sister having a better idea of proper behaviour in company. I think Anne was carefully coached by Lucy as to what she must not say, and Lucy, knowing her sister was probably not sensible enough to keep her tongue checked, listens carefully and amends the remarks to conceal how well they know Edward and how they have learned so much about the Dashwoods.