Character Analysis
Cold Blooded
Mathilde de La Mole isn't the kindest, sweetest person in the world. She might seem that way to the people of upper-class French society, but we readers know that deep down, she's pretty mean.
Even Julien has a tough time negotiating the difference between her beautiful appearance and her cold personality. As the narrator tells us,
She did not attract him. However, when he looked at her more carefully, he thought he'd never seen such beautiful eyes, though they spoke of an enormously cold heart. (2.2.38)
In other words, Mathilde is everything a guy like Julien Sorel needs to watch out for.
It's not always Mathilde's fault that she's a cruel, superficial girl. After all, she's been raised in on of the most socially judgmental societies ever. We get a pretty good sense of Mathilde's whole deal when she's at a social ball and wonders for a moment whether some of the older people there are having a good time. She quickly does a one-eighty and decides that she:
[…] did not care. It was her fixed prejudice never to so much as look at old men, or anyone else well known for saying sad things. (2.9.4)
So in all honesty, the only things she really cares about are 1) being the prettiest girl in the room, 2) torturing the young men who like her, and 3) ignoring anyone who isn't young and beautiful.
Drama Lover
Part of being the most beautiful and most popular girl around is being bored a lot of the time. After all, what are you supposed to do with your time when you've already got it all? Oh yeah, that's right: create drama. Yup, and that's just what Mathilde does. When it comes to creating drama, she tends to get her instructions from romantic novels, as she thinks,
"And I'm still only nineteen! […] This is the time for happiness, according to all these gilt-edged morons!" (2.8.8)
It's kind of funny that she thinks the authors she's reading are morons, considering that she still takes their advice. It's this need for adventure that first makes her pursue Julien Sorel.
Mathilde's need for drama starts out mildly at first, but quickly gets out of hand. After she turns cold on Julien, for example, the guy grabs a sword off the wall and nearly kills her with it. But instead of tossing this guy in jail, Mathilde thinks she's lucky to have such a passionate lover:
Thrilled to the bottom of her soul, Mademoiselle de La Mole could think of nothing but the happiness of having almost been killed. (2.18.1)
Yeesh, come on Mathilde. Have a little sense.
Recognizing Mistakes
Mathilde isn't totally blind to the mistakes she makes in this book. After she's slept with Julien, for example, she reminds herself that:
"He's nothing but a commoner, after all […] His name will always remind me of the greatest mistake of my life. I need to follow, most faithfully, all those popular notions of wisdom, restraint, and honor: a woman has everything to lose, forgetting them." (2.25.37)
Or in other words, she has much more to lose in a sexual scandal than Julien does. He can just leave town, which he's already done with Madame de Rênal. Mathilde, on the other hand, has nowhere to go and will be totally disgraced if word gets out that she slept with a commoner.
After she has fallen for Julien for good, Mathilde has to deal with the consequences of giving her heart to such an unstable dude. For starters, she has to face the fact that in his final days, Julien decides that he actually loves Madame de Rênal more than her. And as the narrator tells us, "Hearing this, Mathilde's jealousy rose to the point of insanity" (2.45.8).
Yes, 19th-century French society is way more unfair to Mathilde than it is to Julien. Julien dies, but that's because he shot a woman twice in church. All Mathilde did was sleep with someone, and her life is practically ruined along with Julien's.
Mademoiselle de La Mole's Timeline