Happily in love as she is, Emma finds herself sympathetic to Frank’s own blunder-filled love story. The letter leaves her with a much-improved impression of him, and she shares it with Mr. Knightley.
As someone who has made and been forgiven many blunders herself by her happy situation, Emma finds herself cheerfully extending such generosity to Frank’s wrongs against her.
Mr. Knightley, too, softens upon reading Frank’s letter, though he still feels Frank’s flaws and his unworthiness in comparison to Jane. Mr. Knightley then proposes to move into Hartfield, in order to avoid disturbing Mr. Woodhouse with his daughter’s marriage. Emma is moved by such a sacrifice on his part, and she approves the plan. Her only regret is for Harriet, whom she feels has undeservedly suffered.
Mr. Knightley’s happy situation in love and new knowledge of Emma’s indifference to Frank also renders him more forgiving towards Frank. His plan to move into Hartfield demonstrates his thoughtfulness in considering Mr. Woodhouse’s feelings, who now won't have to "lose" another daughter.