Here we get a glimpse of Kitty's boudoir: it's "a pretty little pink room," decorated with cheerful porcelain dolls that seem as joyful as Kitty once was. Dolly reflects that this room, decorated just two months ago, shows what a change there has been in Kitty, from happy youthfulness to misery.
Kitty's sitting in a chair looking cold and aloof. Dolly tries to draw her out about her failed relationship with Vronsky.
Kitty becomes furious with Dolly's pity and flies into a rage: she brings the fight to a whole new level when she tells Dolly that she would never do what Dolly is doing, clinging to a man who has been unfaithful.
Dolly goes silent and sad as she thinks of her humiliation and feels terrible that her own sister could throw Oblonsky's treatment of Dolly in Dolly's face.
Kitty hugs Dolly, and tells her sister that she is terribly unhappy. She feels horrible because Princess Shcherbatsky is putting her on the marriage market as though she's up for sale, and now she feels ashamed of herself where she used to feel proud.
Without explicitly saying so, Kitty is sorry for making that comment about fidelity, Dolly forgives her, and knows that she's right about the cause of Kitty's heartbreak.
Dolly is dealing with an outbreak of scarlet fever at home. Kitty offers to help (since she's already had scarlet fever and is thus immune) and goes to stay at the Oblonsky household.
The two sisters nurse all six children through scarlet fever. Kitty's health remains poor, however, and at Lent she goes abroad with her mother.