Emma, Volume I, Chapter 4
Quick and decided in her ways
The narrator tells us right off the bat that Emma is much taken with Harriet Smith, and with the idea of making Harriet a sort of protegée. Emma is "quick and decided in her ways", and I think even first-time readers get a sense of the danger involved in those personality traits as you see Emma inventing a heritage for Harriet that cannot be proved (deciding she must be a gentleman's daughter) and then deciding further to separate Harriet from Robert Martin, despite there being every indication of attachment on both sides.
Emma's logic runs something like this:
I do not associate with farmers.
I want Harriet to be my permanent companion/friend.
If Harriet marries Mr Martin (a farmer), I would have to drop her. (Let's not look closer at that just now.)
Therefore, I must ensure that Harriet does not marry Mr Martin.
Emma goes a step further, however, and begins to talk as if there is no possibility of Harriet marrying Mr Robert Martin, despite every indication that Mr Martin has been courting Harriet - why else would he go so far out of his way just to collect walnuts for her, or drag a shepherd boy into the parlor to entertain her with some songs? And she makes Harriet promise not to associate with Mr Martin's future wife, speaking disparagingly of whomever that would be.
It is the Emma of this chapter that perhaps explains Austen's remarks to her family (according to family legend, anyhow) that Emma is "a heroine whom perhaps no one but myself will like". She is acting in an interfering sort of manner, and in a way that is undoubtedly going to cause her friend Harriet pain - and it's entirely deliberate.
Is she really any better than her father, who tries to boss people around about what they eat and other health matters, as if he knows what's best for everyone? Is she, in fact, worse, since she is deliberately separating Harriet from a young man she obviously has some level of feelings for?
Harriet certainly was not clever
Harriet isn't the sharpest tool in the shed, that's for sure. She is pretty and good-natured and not completely lacking taste or manners, but she's not exactly what you'd call bright - in today's world, we might call her an airhead (or is that term now passé?) She's affectionate, however, and quite attached to Emma, who she both likes and admires. And being a bit dim, she's willing to believe that Emma's judgment is superior to her own.
This can only end in tears.