Dounia (Avdotya Romanovna Raskolnikov)
Dounia is strong and steady, young and beautiful, intelligent and educated. But, because this is a novel by Fyodor "Everyone in the World Is Horribly Flawed" Dostoevsky, she ain't perfect. Dounia is a pretty terrible judge of character.
She learns some lessons over the course of the novel, though, because this is a novel by Fyodor "Everybody's Gotta Learn Sometime" Dostoevsky. In some ways, Dounia is a device used to drive the plot forward. Her relationships with Luzhin and Svidrigaïlov create most of the novel's subplots and contribute to Raskolnikov's decision to murder the pawnbroker.
But, don't worry—she's also much more than a plot device (because this is a novel by Fyodor "Literary Genius Incapable of Writing Two-Dimensional Characters" Dostoevsky). Dounia represents a less depressing view of Russia and the Russian people than we often get in this bleaktastic book. She grows as a character in a less ambiguous way.
Instead of being in a relationship to save someone (Svidrigaïlov) or to escape poverty (Luzhin), she finds a genuine friend, companion, and husband in Razumihin...a man who loves her brother as much as she does and who understands what she's gone through.
Aww. Who says nice guys always finish last?