Elizabeth and Charlotte have a very sincere heart-to-heart conversation early in the novel in which each woman expresses her opinions and attitudes about the subject of marriage. Both women will be in extremely dire circumstances if they don't marry well, but Elizabeth emphatically states that she will only marry for true love. She can't fathom a relationship that is based on anything less, even if it means a life of hardship. She is very idealistic in this regard. Charlotte, on the other hand, is completely practical about the necessity of marriage. She understands Elizabeth's position, but says that for herself, love doesn't matter. She is primarily concerned in finding a man that can support her. She would like a man that will be good to her and for her, but love is not a part of her equation. Elizabeth thinks that she may regret that stand and feels badly that Charlotte is willing to settle for a marriage of convience and financial stability, but she does understand where Charlotte is coming from.
When Collins proposes to Elizabeth she can hardly believe it is happening and she can't turn him down any more emphatically than she does. She really can't stand the man! She is initially dismayed that Charlotte would accept his proposal knowing full well that he is literally rebounding from one proposal to the next, but Charlotte explains again that Collins fits her needs as well as anyone would and that is enough for her. Elizabeth feels bad for Charlotte because this is just not an ideal (full of true love) kind of marriage, but she can't deny that Charlotte will be secure in her future with this marriage. She is ultimately supportive -- even going to visit Charlotte to see how everything is going. Austen uses these two characters are foils to one another to illustrate her theme of marriage and all of the various factors that enter into the decision to marry.
In Jane Austen's novel, Pride and Prejudice, Elizabeth Bennet is one of five daughters in a family that will lose its home when Mr. Bennet dies; at that time, the house will pass to the hands of Mr. Collins, a pastor—who soon comes to visit. Collins hopes to marry one of the Bennet girls. He has recently been assigned a parish so that he will be able to support a wife and family.
Very quickly Elizabeth Bennet realizes that Mr. Collins has decided that he wants her to be his wife. When he does propose, Elizabeth adamantly refuses, believing that a marriage should be based on love and not on making a "good match." However, within three days, Mr. Collins proposes to Charlotte, Elizabeth's best friend, and she accepts.
When Elizabeth hears the news, she is horrified.
Elizabeth is appalled, her mother disconsolate, and Lady and Lord Lucas are ecstatic. (eNotes.com)
Charlotte explains to Elizabeth that just because Mr. Collins was not successful in his proposal to Elizabeth, it does not mean that he cannot find happiness with another woman. So Elizabeth wishes her friend every joy. Charlotte explains to her friend that she has never had the same romantic aspirations of marriage for love as Elizabeth: Charlotte has hoped for an arrangement where she could have a comfortable home and a good husband, believing this would provide her with a marriage as satisfactory as most:
...considering Mr. Collins's character, connections, and situation in life, I am convinced that my chance of happiness with him is as fair as most people can boast on entering the marriage state.
Elizabeth tries her best to come to terms with her best friend's choice. Elizabeth knew she and her friend saw marriage differently, but she is amazed to realize that Charlotte would accept a proposal that did not include affection. Elizabeth is troubled because she believes Charlotte is settling rather than holding out for love, and she is afraid that her friend will never be happy.
Charlotte the wife of Mr. Collins, was a most humiliating picture! — And to the pang of a friend disgracing herself and sunk in her esteem, was added the distressing conviction that it was impossible for that friend to be tolerably happy in the lot she had chosen.
Elizabeth still cares for Charlotte, and is disappointed with her acceptance of Mr. Collins' proposal, but it is simply because she wants her friend to be happy and believes love must be a piece of a marriage for someone to realize true happiness.