Near the end of Pride and Prejudice, Elizabeth uses a simile after telling Jane about how Darcy revealed Wickham’s true character in his letter to her:
“I know you will do him such ample justice, that I am growing every moment more unconcerned and indifferent. Your profusion makes me saving; and if you lament over him much longer, my heart will be as light as a feather.”
Elizabeth says that her heart is “as light as a feather” after hearing Jane talk about how Wickham and Darcy had them all fooled—after all, hearing Jane speak this way takes away some of Elizabeth's guilt about her own misjudgments of Wickham and Darcy.
This moment shows how Elizabeth is becoming aware of her prejudice toward Darcy and is starting to regret all of the ways that she has treated him, including rejecting his marriage proposal. Still, hearing that Jane was also fooled takes away some of her embarrassment. This simile therefore demonstrates how close the sisters are (just hearing Jane affirm her feelings makes Elizabeth’s heart feel much better) while also hinting at how Elizabeth will be able to rebound from her inaccurate judgments and find a way to apologize to Darcy (which she ends up doing later in the novel, eventually leading to their engagement).