which is similar to that of Mr. and Mrs. Bennet.

Mr. Bennet is not pompous conceited etc., he's supposed to be intelligent, and yet he married a woman who had only good looks to reccommend her.
So what was with his *proper way of thinking*?
This should have given Lizzy ample food for thought, about various reasons for which people marry.

I am of the opinion that subconciously :-) Elizabeth formed her principals and opinions based on her parents, and situation at home.
Charlotte has formed her opinion based on her situation at home. She isn't applying principals here as there is nothing contradicting her feelings, thoughts and opinions.

Lizzy here is herself speaking rather narrow-mindedly - and considers her *own* principals and integrity to be the guidance for everyone.

"..prudence for selfishness.."
I wouldn't call it selfish, because selfishness is relative to the harm caused to another while thinking of the gain to oneself, or taking away from another resulting in depriving that person of somethiong while satisfying your own need for it.
Lizzy is harsh here!!!
It is a situation where Charlotte and Mr. Collins both complement each other - an ideal situation for a marriage ;-)IMO

"..meaning of principle and integrity,.."
The meaning as defined by Lizzy?

Charlotte has not compromised her integrity at all. She has already made herself clear earlier her views on marriage.
She has acted on it.
We have to see whether Charlotte shows integrity in her marriage.
I think there lies the test of integrity for her.

"insensibility of danger security for happiness." .."
Again, Charlotte believes that there will be vexations in any marriage, and is ready to face them.
I would say she is not insensible, but self confident.