VATICAN CITY, Oct 10 (Reuters) - Pope Francis on Sunday met a Colombian nun who was freed after being kidnapped by Islamist militants in Mali four years ago. The Vatican said in a statement that Francis met Sister Gloria Cecilia Narvaez in St. Peter"s Basilica just before he celebrated Mass there to open a two-year worldwide consultation on the Catholic Church"s future. read moreThe Mali presidency announced her release on Saturday but the timing and other details were not clear. Kidnapping has been a lucrative source of cash for Islamist groups in West Africa"s Sahel region, where they are waging an expanding insurgency against national armies, French forces and U.N. peacekeepers.