Sanaubar is the sexiest character in The Kite Runner. Baba sounds like a good-looking guy, but really, Hosseini reserves his raciest prose for Hassan's mother, Sanaubar: "I have heard that Sanaubar's stride and oscillating hips sent men into reveries of infidelity" (2.21). (Hmm...we wonder who such men could be? Baba?) The soldiers near the middle school have even heard of Sanaubar and taunt Hassan about her.
Even though Sanaubar doesn't get much time on the page, Hosseini does throw a monkey wrench or two into her character. For one, she sleeps with Baba and then runs off with a dancing troupe, setting in motion most of the terrible things that happen in the novel. (Which is not to say she's to blame – just that she's an invisible influence, much like Amir's mother.) Sanaubar's disappearance obviously affected Amir because he writes about a similar plot in his novel A Season for Ashes. (Actually, he's probably writing about his mother and Sanaubar.)
Sanaubar seems to dislike Ali, her husband, and says she's seen "old donkeys better suited to be a husband" (2.26). We wonder if this might be because of his ethnicity. He's a Hazara like her, but perhaps she is self-loathing. After all, she does sleep with Baba who is a Pashtun (see "Themes: Race" for more). Of course, it could be that Sanaubar is attracted to the power that Baba has and that it has little to do with ethnicity. The novel doesn't go into it, so we can only speculate. In the end, Sanaubar returns to Baba's home and lives with Hassan. She seems to be at peace with her family.