Her saying 'But you are always kind' always seems to me a friendly way of saying, 'don't mention it, I am overlooking your mistake' so to actually bring it up again and draw attention to it would just cause uncalled for embarassment to everyone. Mr K puts a great deal of emphasis on the slight - perhaps this suggests deeper feelings from him on the subject of Emma's bad behaviour? - but Miss Bates is a good bit older and wiser than Emma and she could easily chalk it up to youthful high spirits, (in the same way that I am inclined to) rather than a previously unexplored propensity to evil. We've all been there, and hopefully this will deepen Emma and Miss Bates's friendship. Emma has to take responsibility for putting her foot in it and tries to see Miss Bates as more of an 'equal' - Miss Bates should enjoy Emma's more respectful offer of friendship. Emma is growing up now, and it shows.