This is a question that's been nagging me on this read and through this week's chapters. As you quoted, Elinor thinks she wants to understand Lucy's feelings for Edward.

That's one reason, I suppose, but I still think it's surprising that after the engagement is revealed, Elinor would seek Lucy out and why she would feel and "earnest wish of renewing" that uncomfortable conversation.

We read in ch. 23 that Elinor "wanted to hear many particulars of their engagement repeated again". I suppose this is another chance to catch Lucy in a lie, if she's lying.

But this is the part that really intrigues me: Elinor "particularly wanted to convince Lucy, by her readiness to enter on the matter again, and her calmness in conversing on it, that she was no otherwise interested in it than as a friend, which she very much feared her involuntary agitation, in their morning discourse, must have left at least doubtful."

Why should Elinor be so anxious to convince Lucy she felt nothing for Edward but friendship? Elinor thinks that "she was firmly resolved to act by her as every principle of honour and honesty directed, to combat her own affection for Edward and to see him as little as possible; she could not deny herself the comfort of endeavouring to convince Lucy that her heart was unwounded."

If it's a matter of honour, does Elinor feel ashamed that she fell for someone who was already taken? It's funny that Elinor would think it a principle of 'honesty' when she is deliberatly setting out to convince Lucy of something that is not at all true.

Does Elinor think it would be a comfort to convince Lucy that her heart was unwounded because Lucy was trying to hard to hurt her?