My GR focus is Emma and Harriet's relationship, but in the first week other people posted everything I had to say, which meant I could be lazy :). However, I have been thinking about the similarities and differences between how Emma manages Harriet, and how she manages her father and Isabella.

Emma uses diversion a fair bit in both relationships:
"Now he has got my letter," said she softly. "I wonder what they are all doing -- whether his sisters know -- if he is unhappy, they will be unhappy too. I hope he will not mind it so very much.

"Let us think of those among our absent friends who are more cheerfully employed," cried Emma. "At this moment, perhaps, Mr. Elton is shewing your picture to his mother and sisters, telling how much more beautiful is the original, and after being asked for it five or six times, allowing them to hear your name, your own dear name." (chpt 7)

"The carriage! But James will not like to put the horses to for such a little way; and where are the poor horses to be while we are paying our visit?"

"They are to be put into Mr. Weston's stable, papa. You know we have settled all that already. We talked it all over with Mr. Weston last night. And as for James, you may be very sure he will always like going to Randalls, because of his daughter's being housemaid there. I only doubt whether he will ever take us anywhere else. That, was your doing, papa. You got Hannah that good place. Nobody thought of Hannah till you mentioned her -- James is so obliged to you!" (chpt 1).

And this is a particular form of diversion - she creates a happier flow of thoughts.

She also uses other people's concerns for her:
"Indeed, Harriet, it would have been a severe pang to lose you; but it must have been. You would have thrown yourself out of all good society. I must have given you up."

"Dear me! How should I ever have borne it! It would have killed me never to come to Hartfield any more!" (chpt 7)

"Come, come," cried Emma, feeling this to be an unsafe subject, "I must beg you not to talk of the sea. It makes me envious and miserable; I who have never seen it! South End is prohibited, if you please. (chpt 11)

Now the two situations are a bit different, when talking to Harriet, Emma's statement about loss of friendship is also an implicit threat to Harriet, while I have not been able to find any moment where Emma even implicitly threatens her father with a bad outcome. This shows some skill on Emma's side, as her father would most likely fall apart if confronted with any such threat.

A third tactic is establishing a presumption, if I am right in seeing a similarity between two passages in chapter 7 and chapter 1:
"Yes. But what shall I say? Dear Miss Woodhouse, do advise me."

"Oh, no, no! the letter had much better be all your own. You will express yourself very properly, I am sure. There is no danger of your not being intelligible, which is the first thing. Your meaning must be unequivocal; no doubts or demurs: and such expressions of gratitude and concern for the pain you are inflicting as propriety requires, will present themselves unbidden to your mind, I am persuaded. You need not be prompted to write with the appearance of sorrow for his disappointment." (chpt 7)

"A house of her own! -- but where is the advantage of a house of her own? This is three times as large. And you have never any odd humours, my dear."

"How often we shall be going to see them and they coming to see us! We shall be always meeting! We must begin, we must go and pay our wedding-visit very soon." (chpt 1)

These two are a bit different situations, in one Emma is responding to a question from Harriet, Emma's response creates a presumption about what the reply will be, in the other Emma is responding to a comment by her father, and is busy establishing the presumption that the Woodhouses will be calling on the Westons very soon. Different situation, but the similarity still strikes me.