Several posts have already been made listing Emma's good qualities. To all this I must add Emma's skill as a peacemaker. Not only des she keep the peace at home by managing her father's tendency towards depression and querulousness, she makes peace during sticky situations. To be so young, and yet have the talent to diffuse tension, is admirable. Her skill and tact at handling such situations are matched by very few people.
We all saw in Chapter 12 how Emma parried and diverted "dangerous" topics when Mr. Woodhouse and poor clueless Isabella were discussing sea-side trips and their favorite apothecaries. It was also nice that she seemed to have an unspoken partnership with Mr. Knightley to help maintain family peace.
Again, in Chapter 15, Emma and Mr. Knightley work together and quicky resolve the scene of confusion that has resulted from Mr. John Knightley's naughty side.
Finally, even though she is insulted and upset over Mr. Elton's proposal in the carrige ride back home, she still refuses to part with him without a "good night".
Unfortunately, it is another aspect of this skill that helps Emma in manipulating Harriet. Her talents can be used for good and bad. It is not Emma's personality that needs to change, but her attitude.