] I also think this is yet another example of how deeply attached Elinor is to Marianne.

Yes. This is one of the things that makes me actively like Elinor. I admire her and respect her for her good qualities of self-control, tact, etc. but it's her very strong affection for her sister that carries me across the line into liking her and thinking of her as a person I'd like to meet and spend time with if that were possible. It says a lot for Elinor that she doesn't merely tolerate her sister but truly loves her, in spite of her exasperating habits.