why does mariam go to herat, and what happens to her there?

Maiam wants Jalil to taker her to a movie in Harat. On the day of the movie, Jalil does not come to pick up Mariam, so Mariam decides to walk to Herat herself. Once there she is amazed by the city, and she catches a ride to Jalil's house. Mariam is told by a doorman that Jalil was away on business indefinitely and that she should go home. Mariam refuses to leave and spends the night outside of Jalil's house.The next day, Mariam tries to run into the garden. She only catches a quick glance of Jalil in the window, before she is forced into the backseat of Jalil's car by his chauffeur. Mariam is taken back to the kolba, betrayed and ashamed. While walking back to the kolba, the chauffeur tries to hide Mariam's eyes, but Mariam is able to see that Nana has hanged herself.