The scene in which the family is informed by the manservant that Lucy Steele is now Mrs. Ferrars. Even though she's long been reconciled to the situation, it doesn't keep Elinor from turning pale and almost fainting, and Marianne is so upset by her sister's condition that she almost faints.
Once this is all cleared up, it's followed by an equally painful but much quieter scene in which Elinor and her mother are left alone together, and Elinor can't even speak because she's in so much pain. It forces Mrs. Dashwood to finally admit to herself that she has (quite unintentionally) been almost unkind to Elinor about the whole thing, because she's been so busy worrying about Marianne that she let herself believe Elinor was all right.
The 1995 Film
Elinor's desperate speech to Marianne when the latter learns that Edward has long since been engaged to Lucy Steele. From someone normally so reserved, it's absolutely shattering.
Elinor: What do you know of my heart? What do you know of anything but your own suffering? For weeks, Marianne, I've had this pressing on me, without being at liberty to speak of it to a single creature. It was forced on me by the very person whose prior claims ruined all my hopes. [sobs] I have endured her exultation again and again whilst knowing myself to be divided from Edward forever. Believe me, Marianne, had I not been bound to silence, I could have produced proof enough of a broken heart even for you!
When the doctor tells Elinor she should prepare for the worst, Elinor breaks down at Marianne's bedside and begs her not to die. Different as they are, Elinor can't live without her younger sister.
