We're going to let you in on a little secret—Mariam is the real hero of A Thousand Splendid Suns. At first glance, you might be tempted to think of Laila as the novel's hero. She's the one who survives the events of the novel, and she's the one with great things in her future. Why wouldn't she be the hero? Well, you just need to take a closer look.
Mariam changes more than any other character over the course of the novel. At the start, she is a harami from a small village without much hope for the future. As a harami, she's forbidden taking part in "the things other people had, things such as love, family, home, acceptance" (1.1.6). Jalil and Nana are Mariam's only family, and their relationship is anything but healthy.
Mariam finds the family that she never thought she'd have in Laila and Aziza. Mariam becomes a mother figure to Laila—she even frequently identifies herself as Laila's mother to other people. Mariam had already given up on finding happiness, so she's as surprised as anyone when she finds Laila.
Laila and Mariam are like peanut butter and jelly. Sure, they're great on their own. But together they become more than the sum of their parts. Laila brings her headstrong nature to the table, giving Mariam the confidence that she so desperately needs. Mariam, on the other hand, has an inner strength that's "as hard and unyielding as a block of limestone" (4.50.12). The combination of the two is something fierce.
Mariam hasn't been confident in herself since she was a child. As an illegitimate child, she was always an outsider, and the final straw may have come when Jalil rejected her. After that, she seemed to cut herself off from the people around her as a defense mechanism. But Laila plants something inside her. Mariam might not know what it is that's growing inside her—she might even think that it's just the "twin poisonous flowers" called love—but, believe us: it's sure going to sprout (3.35.26).
Laila's inspiration helps Mariam take control of her own destiny. Rasheed has been an awful, abusive husband to her, but up until this point, she's never defended herself. But when she sees Laila being strangled to death, she finally understands the need to fight back. And she does, killing Rasheed and selflessly taking the rap for the crime so Laila can live on.
Mariam is able to become what she thought a harami like her could never be: a mother, a friend, and a hero. In a perfect world, Mariam would be able to live out a natural life with Laila and her family. But heroes, like Mariam, know that the world isn't perfect. The only thing you can do is do what's right by the people you love. Mariam, for her part, is simply grateful for the opportunity to know Laila and her children for as long as she could. It's only because of her heroic actions that Laila and her family are able to survive and work for positive change in Afghanistan.