Mrs. Weston was the object of a regard, which had its basis in gratitude and esteem. Harriet would be loved as one to whom she could be useful. For Mrs. Weston there was nothing to be done; for Harriet every thing. (Chapter 4)

In her kindness to guide and do every thing for Harriet, Emma does a terrific job trashing Mr. Martin in Chapter 4, a quick review of the attack:

He is pain, entirely wanting in gentility, so very clownish and totally without air, illiterate and coarse with an awkward look and abrupt manner. When he grows old he will be a completely gross, vulgar farmer, inattentive to appearances and thinking of nothing but profit and loss. Emma even goes so far to predict poor Mr. Martin is destined to marry a vulgar stupid woman who Harriet must not consort with because she must be careful of keeping odd acquaintances.

After the clobbering is over, still Chapter 4, Emma then regales Harriet with personal praise she solicited from Mr. Elton which gets her to blushing and smiling and admitting she always thought him very agreeable.