Madame Stahl is an invalid who raised Varenka as her own daughter. Varenka is beloved by everybody for her good manners and fine upbringing, and she charms Kitty and the Princess, Kitty’s mother.
Even though Varenka is not Madame Stahl’s natural daughter, she has become beloved by all for her impeccable manners and lovely demeanor.
One day, Varenka is singing as Kitty accompanies her, and she hesitates before singing a particular song; she later reveals that that is the song she sang to her lover. They were planning to be married, but his mother called off the wedding. Kitty asks about the situation, obviously asking about herself, and Varenka tells Kitty that there are more important things than insults: what matters is whether or not Kitty still loves the man.
Varenka, like Kitty, has also had heartbreak in her life: her lover’s mother forbade him lover from marrying her because of Varenka’s lower social status. Unlike Kitty, who is still deeply ashamed of her episode with Vronsky, Varenka has attempted to put the insult behind her and move on.