Mr Elton's wedding plans
Mr Elton returns to visit everyone and be smug about his conquest - a woman with 10,000 pounds to her name, who is more than happy to marry him and move to Highbury. He pays no attention to Emma and is obnoxious to Harriet, and then leaves to get married.
Emma begins to question what she ever found pleasing about him, and on learning more about his intended spouse - a Miss Augusta Hawkins - she believes that Harriet is inferior to Miss Hawkins only in lacking money. (We shall soon have a chance to see whether Emma proves right on that count.) Turns out Miss Hawkins's father was in trade as a merchant, her uncle is an attorney, and her sister is married to a guy who owns two carriages, and that's pretty much it for her backstory. (I can't help but notice that her background is not too different from some Austen characters we already know - the Bennet sisters had an uncle in trade and another that was an attorney, after all; but they were the daughters of a gentleman, and Miss Hawkins is not.)
Could she but have given Harriet her feelings about it all! She had talked her into love; but, alas! she was not so easily to be talked out of it. The charm of an object to occupy the many vacancies of Harriet's mind was not to be talked away. He might be superseded by another; he certainly would indeed; nothing could be clearer; even a Robert Martin would have been sufficient; but nothing else, she feared, would cure her. Harriet was one of those, who, having once begun, would be always in love.LOL! The narrator's points here are hilarious, telling us much about Harriet - and, in fact, largely nailing Harriet's character with that final observation: Harriet "would be always in love" is a fine bit of foreshadowing, whether Emma realizes it or not.
Emma continues to meddle
Harriet has been invited to call on Elizabeth Martin, and Emma is scheming as to how to have Harriet call without the possibility of Harriet spending too much time with the Martins. She doesn't really want Harriet to renew her acquaintance with the Martins, even though she understands the necessity of Harriet paying the call, because she believes Harriet will renew her feelings for Mr Robert Martin, marry him, and then Emma would be "forced" to cut off the relationship.
Mind you, the only person who would force her to cut off that relationship is Emma herself, but she doesn't seem to pay much attention to that.