For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Mr. Darcy insults Elizabeth in range of her hearing, then starts falling in love with her.
Act II
Mr. Darcy proposes and gets rejected. He gives Elizabeth a letter that throws many of her assumptions and beliefs into question.
Act III
Darcy's proposal, round two – he's accepted.