you in your post Barbara, are things which Emma possessed even before. She just didn't apply them in every situation IMO.

>"Emma could not bear to give him pain. He was wishing to confide in her -- perhaps to consult her; -- cost her what it would, she would listen. "

Emma tries her best not to give any pain to people she loves.
In this case there is the extra knowledge that she would be giving pain to the man she loves.

The BOx HIll fiasco taught Emma to apply this already existing character of hers to Miss Bates as well.
Having kind thoughts about Miss Bates is now an extension of her kind thoughts about some other people in her life.

>She realizes that she has said something that is perhaps not something to have said, pauses and gets beyond her own feelings to consider someone else's. She's gotten beyond it being all about Emma. [emphasis is mine]

This is again about Mr Knightley.
Anyway she did this during that period of Elton fiasco regarding Harriet. CH:17;

Her second duty now, inferior only to her father's claims, was to promote Harriet's comfort, and endeavour to prove her own affection in some better method than by match-making.

Of course her father occupies first place always, it makes this character as ever present in her - she has to extend it to others where she didn't before.

Same goes for recognizing 'the ungracious stopping', though I think with Mr Knightley (or anybody else for that matter)she would have apologized for this even earlier if she ever cut him/them mid sentence in her enthusiasm.
We can't say Emma lacked manners, I think.

As far as Jane is concerned, we have still to find out whether Jane's behaviour was normal and not overly reserved, or that she was not to blame at all, and that Emma should take all the blame for that evening as being ungracious, because being gracious is Emma's strong point, though she fell short at Box HIll.