"I think Harriet was already under the influence of this 'high/low' thing with all that gossip going on at Goddard's. "

EVERYBODY was "under this influence". People tried ot marry as well as they possibly could. THey saw marriage as a way of advancment and of improving their family's postion. THey were conscious of their social position in a way that seems OTT to us now but it was common then....
I dont see that Harriet is being friends with Emma becuase she hopes to get a better offer of marriage. Emma picked her up and chose her as a friend, THEN put ideas in her head that she coudl marry a gentleman. She has worked on her to help her see that Robert Martin ISNT a gentleman and that she coudl do better. Harriet is not "in love" with Martin, she's fond of him and likes him and left to herself she would problaby have spent more time iwth the Martins, grown to love him more and accepted his offer of marriage. But Emma took her up and interfered.

To her, Emma's social dictats have almost the force of a royal command, just as Lady Catherine's opinions have with Mr Collins. But then agian I'd say very few girls in her position would not be pleased and flattered by the notice of a woman like Emma and would not be better pleased ot have a chance of marryigng a well to do gentleman rather than a farmer....

I dont see that Harriet shoudl have to marry RObert or remain best friends with the Martins just because she was friends with teh girls at school and spent a holiday with them. She certainly should not drop them rudely, and when Emma presses her to cool down the freindship, she does so clearly with some discomfort. She is a little at fault but not so much as Emma. After all Emma is the social superior, if SHE tells her that it si right to cool off her friendship with the Martins, who is harriet to say no to her???
but generally speaking, people do move on and lose soem friends and make new ones. If there was not the social issue, I dont see why Harret should remain best friends iwht the Martins for life or feel obliged to marry inot the family becuase of a shcoolgirl friendship.