Emma is surprised enough by Mr. Elton's 'strange insensibility' to Harriet's illness to wonder if John's warning might be correct ('-- Absurd and insufferable!' -- '), but she's more annoyed during 'the most overpowering period of Mr. Elton's nonsense' because she can't hear what is being said about someone else:
Now, it happened that in spite of Emma's resolution of never marrying, there was something in the name, in the idea of Mr. Frank Churchill, which always interested her. She had frequently thought -- especially since his father's marriage with Miss Taylor -- that if she were to marry, he was the very person to suit her in age, character and condition...she had a great curiousity to see him, a decided intention of finding him pleasant, of being liked by him to a certain degree, and a sort of pleasure in the idea of their being coupled in their friends' imaginations.
More matchmaking! :) I can see why the screenwriters handle it this way...it's much more dramatic, and broadly funny, to have Mr. Elton jump Emma in the carriage, but then again the way this is handled in the book is more subtly humorous, and it presages the scene where the other Mr. Knightley asks Emma if she truly understands Frank Churchill's relationship with Jane Fairfax.
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