I like seeing this fiesty side of Elinor, it makes her so much more human, doesn't it?

She sees so clearly that Lucy is "illiterate, artful and selfish" but also recognizes that she is quite clever and cunning. So while Lucy gets in her zingers, she also knows that Lucy will "get" the barbs aimed at her, but will play her role of selfless Penelope for all its worth. This gives Elinor a bit of freedom, doesn't it? And she takes advantage of it. Good for her, I say!