Or a spider in her web.

Notice who her select few are:
- Mrs Goddard, who knows the intimate details of at least forty, if not all, the educated young women in town.
- Miss and Mrs Bates, who have for several decades held the social privilege of the parson's family vis knowing every hatching, latching and dispatching in the district, and such essentials as who the godparents/bridesmaid/pallbearers were. Being the parish memory gives the Bates valuable social capital, both in their former office of building a christian community, and their current one as a hub of gossip within it.
- Mr Elton, the highly social current incumbent and purveyor of parish news.
- Mr Perry, who, like Mr Elton, has a profession that enables him to cross social boundaries freely.
- Mr Knightley, who is regarded as a general friend and advisor, and is particularly connected with the farming interests of the area.
-Mr Weston, who is highly social and has particular connections with the tradespeople of Highbury.

Thanks to her select few, Emma has already discovered "all that was generally known" about Harriet's history (and as much as Harriet knew herself). I bet Harriet is not the only member of Mrs Goddard's household that Emma knows well by sight.
Emma can make some well educated guesses about Robert Martin's capital from what she knows about him via Mr Knightley, too.

For all her isolation, Emma shows a detailed knowledge of her neighbours, and an interest in them that seems to me rather regal, and possibly more than they have in her.
She might affect to be above the schoolgirls and the yeomanry, but I am sure she enjoys the new view of their lives that Harriet carries to her.