Mrs. Bennet. Mrs. Bennet vies with Mr. Collins for the honor of being the most absurd character in the book, and it is all too easy to malign her, as her husband is inclined to do with his dry wit. The plain fact, however, is that Mrs. Bennet understands the gravity of her daughters’ situation and realizes how imperative it is that they should marry. In this respect, she is a far better parent than Mr. Bennet, whose idleness and failure to provide for his daughters make him a poor father, although an indulgent one.

Mrs. Bennet’s desperation to marry off her daughters is strong enough to change every opinion she has and to reverse every decision. She detests Mr. Collins on principle until he shows signs of wanting to marry Elizabeth. She then likes him instantly. Exactly the same is true of Mr. Darcy. Every decision Mrs. Bennet makes (or forces her husband to make) is motivated by the desperation to marry off her daughters and (in the case of Lydia) to save them from disgrace. She may be a foolish, ignorant woman, but, in this respect, Mrs. Bennet is a solicitous and dutiful mother.

The previous educator commented on the desperation of Lydia, and that's a great choice. From a different angle, Charlotte Lucas is in a desperate position and makes a matrimonial choice as well.

Mr. Collins is one of the most vapid and self-serving characters in all of literature. Yet somehow, he acquires the hand of Charlotte, who is Elizabeth's friend. Charlotte is sensible, intelligent, and gracious. So what leads her to accept a proposal from such a seemingly poorly-matched husband?

She's old—at least for that era—and does not have any other offers of marriage in the wings.

Therefore, she's in a fairly desperate position. She doesn't want to end up completely alone, because of the inability of women to own property or money in her historical context. And there is a possibility that there won't be another proposal in her future. She lives out in the country, where there isn't even great opportunity to create social events. Elizabeth is aghast at her friend's choice, convinced that Charlotte can never be happy in her desperate grasp for Collins.

Yet Charlotte herself is willing to create a different version of a "happy" marriage:

I am not romantic, you know. I never was. I ask only a comfortable home; and 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.

Put into a desperate situation, Charlotte weighs her odds and potential outcomes and decides that being married to Mr. Collins will at least bring her security—and there is worth in that choice. She isn't the silly, desperate young girl that Lydia is. Instead, she is intelligent and calculating, not romanticizing the situation but using her desperate conditions to make the best choice possible. Though her friend may see Charlotte's desperation as leading her to making a bad choice, Charlotte herself is comfortable in the choice she makes.

Regarding Jane Austen's Pride and Prejudice, the adage "Desperation is the surest path to making a decision, good or bad," means that when one is desperate and is forced to make a decision in haste or due to extenuating circumstances, a decision may be good or bad because a form of anxiety has pushed the issue.

We see this is when Lydia and Wickham run away. At first this is concern by the family that they may have married, but then there is real fear that, in the face of scandal, they may not have married. The desperate choice on Lydia's part is not a good decision, but there is hope that it may be "fixed" if they have at least married to avoid Lydia's reputation being irreparably damaged.

Elizabeth receives a letter from Jane that reports Lydia's "desperate" act:

By this time, my dearest sister, you have received my hurried letter; I wish this may be more intelligible, but though not confined for time, my head is so bewildered that I cannot answer for being coherent. Dearest Lizzy, I hardly know what I would write, but I have bad news for you, and it cannot be delayed. Improdent as marriage between Mr. Wickham and our poor Lydia would be, we are now anxious to be assured it has taken place, for there is but too much reason to fear they are not gone to Scotland...

The reference to Scotland is Gretna Green, a place outside of England where young people could elope and be married immediately. With marriage and the consummation of the marriage, a young woman and man could avoid their parents' refusal to give their blessing to a marriage at home.

In this case, ironically, the desperate move to run away and be married is no longer the worst that could happen; if they ran away and did not marry, Lydia's reputation would be so damaged, that making a good marriage for her would be impossible.