The dual aspect of Raskolnikov's personality is exemplified again when Raskolnikov is drawn to Sonya enough to make his confession, but after having done so, he is suddenly repulsed by her. Part of his repulsion is due to the fact that he dislikes her ideas about suffering and more importantly that he needs to go to prison.
In addition to confessing to Sonya, he also wants to confess his crime to his sister. The idea of confession has been constantly with Raskolnikov since moments after the murder.
The death of Katerina leaves Sonya responsible for the children. Rodya had foretold this to Sonya and now it is true. Consequently, Svidrigailov shows up, and the money he had once intended for Dunya will now go to Sonya and the children, which will free Sonya financially to follow Raskolnikov to Siberia.
