I see her as a bossy lady who wants everyone to act according to her admonitions.

If there is no interaction with anyone else, it only means that no-one but Elizabeth "with her easy playfulness" feels equal to arguing with her... However I would not bet that lady C is clever enough to enjoy contradiction, though maybe she invites her to stay a month longer to keep from the boredom of Mr Collins' company after the departure of her nephews... It is likely that her imperiousness has scared off all potential company in the neighbourhood.