"Was she indifferent to the opinion of a stuffed shirt jerk?"
Well, I think she was not, and checked her birthing attraction with her humour, and repeating his words all around.
This has been much discussed in the Pride and Prejudice board.
"Is that why she feels that she must be impertinent so that she does not grow afraid of him?"
I have read that she did grow a bit afraid of him, because, having, with her father, always been among the "wit predators", she had a hint of how uncomfortable it could be to be a prey, like her mother. I like very much this idea.