In The Kite Runner, Hosseini uses Khanum Taheri to reflect how marriage is fundamentally transformative for Afghan women. He also uses it as a statement about cultural practices that must stop.
Prior to marriage, singing was a part of Khanum Taheri's life. However, once she marries, she is forced to stop because her husband orders it as part of the conventions of marriage. Symbolically, this shows how the social mores that concern marriage in Afghanistan force women to stop singing their own songs. Khanum does not fight this condition. In fact, she does not fight much in her marriage, accepting the conditions within which she must live. It is sad to think that such a passionate part of Khanum's life has been taken away because of the institution.
The significance of Khanum Taheri's sacrifice reflects that oppression is not merely present in the Taliban. What the Taliban do to Afghanistan takes place on a social and political level. However, Hosseini is suggesting that the mentality that the Taliban use to deny voice and consolidate power is embedded in private aspects of the culture. Hosseini believes that cultural practices which empower one person to take away the dignity of another must stop. Whether it's Assef doing unspeakable things to Hassan because he has the power to do so or General Taheri preventing his wife from singing in public, the repressive elements within specific cultural practices must cease. This statement is amplified through Soraya's rebellion.