MAQLUBA, Iraq — The young Yazidi girl rocked apprehensively as she described the ordeal that took her from her family, snatched from her home by militants in Iraq, then sold as a slave in Syria before finally escaping to Turkey. The 15-year-old is now with what is left of her family — two of her brothers and some more distant relatives — living in a makeshift roadside shelter in this tiny village in northern Iraq, along with other families shattered by the onslaught from the Islamic State militant group.