She represents the passivity, irrationality, slackness, and submissiveness of the "Eastern" mentality. Her casualness and sloppiness are outward signs of her inner softness. She dislikes Settembrini and Naphta because they are not "human" (emotional) enough for her, makes fun of Joachim because he is steadfast and uses foresight in his planning, and loves Mynheer Peeperkorn because "his feeling forced me to follow and serve him."
As the temptress of Hans Castorp, she is Settembrini's adversary. Her lure is of a purely physical nature, and her disease enhances it. Her irrationality has the twin features of submissiveness (toward Peeperkorn) and seductive power (toward Castorp and Wehsal, a minor rival of Castorp).
There is no doubt that, in Mann's scheme of "Western" and "Eastern" values, she stands for the danger of disintegration threatening Germany (Castorp) from Russia. This should not be taken as Mann's attempt to reject or even discredit the Soviet revolution which was in the making when he wrote the novel.
Clavdia Chauchat's traits are negative in that they distort her personality and not because they are different from those of, say, Settembrini. Her whole laissez-faire attitude toward life is bad only because she overdoes it, just as Settembrini's intellectualism is bad only because it is exaggerated.