In A Thousand Splendid Suns, Miriam's last name is not explicitly provided to the audience.
Character Naming Conventions in the Novel
The narrative style of Khaled Hosseini's A Thousand Splendid Suns focuses primarily on the personal lives and journeys of its characters, referring to them almost exclusively by their first names. This means that last names are not disclosed for any of the characters in the novel, including the protagonist, Miriam.
Even when Miriam marries Rasheed, a common social custom would suggest a change in her last name; however, the book never provides her with a new surname, nor does it reveal what her maiden name might have been. The absence of last names is a deliberate choice within the storytelling, directing the reader's attention to the individual experiences and relationships without the formality or societal context often implied by surnames. Therefore, readers are never given a last name for Miriam or any other character in the story.