In the first passage, I take it that Elinor is impervious to Mrs Ferrars's petty nastiness, but does care how her sister's feeling. It's hard to say whether she'd mind being defended by a well-informed friend against something she did find directly hurtful. We don't get any actual examples of that, do we? So I'm inclined to look to chapter 37 where Elinor accepts sympathy from Marianne, and say that she'd probably accept other kinds of well-informed support too.

In the second passage, what could Elinor possibly say or do that'd get through to Lucy, short of publicising the secret engagement? I don't think she'd resort to that, again because of something that comes out in chapter 37: "... I acquit Edward of all essential misconduct. I wish him very happy; ...; and time and habit will teach him to forget that he ever thought another superior to her."** That's not the sentiment of someone who'd trigger a crisis around Edward in retribution for one snide remark.