The widow of a slain Islamist militant leader will be charged for allegedly using social media to recruit Islamic State sympathisers to join a five-month siege of a southern city, Philippine authorities said Friday.Hundreds of local and foreign gunmen who had pledged allegiance to IS rampaged through Marawi, the principal Islamic city in the mainly Catholic Philippines, starting in May -- sparking the nation's longest urban war that claimed more than 1,100 lives.