AMINA was one of the hardest-working girls in her class at Sayed Ul-Shuhada High School in west Kabul, her best friend remembers, determined to become a doctor to treat Afghanistan's thousands of war victims. Amina became a victim herself on Saturday, killed in a massive bomb blast as she and dozens of girls left school in the minority Hazara neighbourhood that has repeatedly been targeted by militants. Masooma, 17, who was holding back at school with friends, narrowly missed the blast. "It was like the sky was falling in," she said. Mourning her friend, Masooma is now torn between fear…