Reading the book this time, I see it as a caution against acting outside one’s scoop or circle. If Emma had befriended Jane, not Harriett, she would have been acting more appropriately. Though, I’m not sure how intended or well this moral is conveyed. It’s clear that the narrator and Emma are very different people, the narrator often pokes fun at her. Yet, there re moments when the pov shifts to Knightly, the proposal, as if the narrator is not privy to Emma’s true inner workings. Practically, I think this is Austen having a bit of a block. It does give some interesting food for thought. 

Knightly was correct, Emma built herself a feedback loop that sang only her praises. Her ability to accept that she acted poorly or was in the wrong is what I think saves her character from being irredeemable. The ending is a pretty wrapped package, but unique in how Knightly, so often a mentor to Emma, accommodates to her needs rather than asking her to bend to custom.