I don't think Emma really understands the possible serious effects of her meddling and great mistakes in wanting to arrange Harriet's life. What makes me feel that Emma had really learned very little is this part --

"Here have I," said she, "actually talked poor Harriet into being very much attached to this man. She might never have thought of him but for me; and certainly never would have thought of him with hope, if I had not assured her of his attachment, for she is as modest and humble as I used to think him. Oh! that I had been satisfied with persuading her not to accept young Martin. There I was quite right. That was well done of me; but there I should have stopped".

Emma still thinks it was perfectly "right" and "well done" to have persuaded Harriet not to accept Martin! She never had a thought of -- if she was so wrong about Elton, might she also have been mistaken about Martin?