Charlotte is Elizabeth Bennet's best friend. She's introduced as a "sensible, intelligent young woman, about twenty-seven" (5.2). So Charlotte's principle characteristics, we're told in that first description, are that she is a) sensible, b) intelligent (both good things in Austen's opinion), and c) that she's…27? In Austen's time, to be a 27-year-old woman and still unmarried is bad news – a single woman past 25 who is neither particularly pretty nor particularly rich is on the fast track to spinsterhood.
There are a couple of different tacks to take about Charlotte. The most obvious one is her super-practical, almost robotically logical approach to marriage. She wants to get out of her parents' house, and she's not getting any younger, so she basically just hooks up with the gross Mr. Collins, fully aware that neither of them is going to make the other happy, but also knowing that he is probably her last chance to be the mistress of her own house. Wow, that's a long sentence. Take a deep breath. Anyway. What do you think about her decision – does it make her somewhat more empowered as a woman? Or is this just spelling out how limited women's choices were back in the day?
Another way to think about Charlotte is as another counterpoint to Jane. Jane is quiet and shy and doesn't go for what she wants. Charlotte, on the other hand, has no problem making it clear immediately to Mr. Collins that she's up for it if he is. Charlotte gives telling advice on the subject of marriage early on. When gossiping with Elizabeth about just how much of a crush Jane has on Bingley, Charlotte says:
If a woman conceals her affection with the same skill from the object of it, she may lose the opportunity of fixing him; and it will then be but poor consolation to believe the world equally in the dark […] In nine cases out of ten, a woman had better shew more affection than she feels. (6.2).
Shortly after, Charlotte also gets in that famous line, "happiness in marriage is entirely a matter of chance…It is better to know as little as possible of the defects of the person with whom you are to pass your life" (6.8). Elizabeth laughs at her, and says, "you would never act in this way yourself."
As we know, though, that's exactly what Charlotte does. After Elizabeth rejects Mr. Collins, Charlotte accepts him, even knowing that she's only his second choice (third, actually, since Mr. Collins initially had his eye on Jane). How did Charlotte manage to get a marriage proposal out of Mr. Collins the day after he'd been rejected by Elizabeth? We don't really know, because Austen doesn't narrate the proposal scene. Does Charlotte recognize that his business in town is wife-hunting, and deliberately flirting in the way that she suggested that Jane should do with Bingley? Maybe.
That's not all! We have even a third idea about what Charlotte's point in the novel is – she is another lesson in empathy for Elizabeth. Check out how horrified Elizabeth first is when Charlotte tells her she's going to marry Mr. Collins. Seriously, she almost throws up a little in her mouth. Then, after she goes to visit the Collinses, Elizabeth slowly realizes that not everyone has to live life the way she would want to, and kind of gets a better sense of her friend.
Charlotte Lucas Timeline