My Mother would like to visit me in Istanbul, her flight is Miami-Frankfurt-Istanbul. Due to her Colombian nationality, does she requires a transit visa?
Colombian nationals do not need a visa to transit at a Schengen airport, including Frankfurt, provided they don't need to leave the international arrival lounge. See Do I need a visa to transit (or layover) in the Schengen area?
There are also plans to allow Colombian nationals to enter the Schengen area without visa but I am not entirely sure of the current status of all this. The relevant legal text has been amended but the EU also needs to conclude a visa waiver agreement with Colombia (a whole process in itself) and the official website still lists Colombia as a country whose citizens need a visa.