about the grubbiness.

That she told FC about it is what is wrong about the whole thing in addition to mixing fact and reality, which results in her opinion of Jane which *seems* to Emma to be supported by things she sees, which of course could mean something else.

-Jane's more than normal reserve (also noted by Mr Knightley)
-her insistence on staying at Highbury *in winter* to cure her cold instead of accompanying the Campbells to Ireland where she would have better chances of recovery
-her smiles when apparantly there is nothing to smile about
-the appearance of a piano out of thin air