HOUSTON - On a blustery night the week before Mother's Day, a woman and her daughter sat together on the sofa at a hair salon here. Nica Sabet had come to the beauty parlor after school, because it was where her mother, Nahid Sabet, worked. By this time, past 8 o'clock, the doors were locked and the customers gone, and Mrs. Sabet could tell the story that Nica had never heard in its entirety...The story, as revealed over several hours by Mrs. Sabet, began on the day 40 years earlier in Tehran when, as a 15-year-old, she converted from her family's Muslim faith to the Bahai religion...