Charlotte and Elizabeth are best friends. They adore one another. They enjoy their moments of criticizing Darcy. Both of these women are strong individuals who can see clearly the outward shallow appearances of others.
Elizabeth is very aware of the character of others:
She is quick to recognize most people's principal characteristics—for instance, she recognizes the stupidities of many members of her family and quickly characterizes Lady Catherine de Bourgh as a control addict and her sister's suitor Charles Bingley as a simple and good-hearted young man.
Charlotte is very perceptive as well. When Darcy makes a critical comment about Elizabeth, Charlotte comes to her rescue. She tells Elizabeth that Darcy is not to be acknowledged in his criticism.
Both Charlotte and Elizabeth enjoy each other's company so much. They are very observant. They are keen observers and can clearly judge the character of others. They recognize the shallowness of Mr. Collins.
When Charlotte tells Elizabeth that she is to marry Mr. Collins, Elizabeth loses respect for her friend Charlotte. Charlotte is no less able to judge character in others. She just appears desperate to find a husband. She worries that her parents will have the burden of taking care of her through her older years.
Elizabeth is confused as to why Charlotte would put aside her good judge of character and marry someone like Mr. Collins.
Elizabeth and Charlotte reunite when Elizabeth goes for a visit to the Collins' residence.