Angels don't exist. Any type of winged creature that's not a bird or an insect doesn't exist - at least if you ask most people. People are narrow-minded and so many of them does not believe what they cannot explain. Some people know better. A secret organisation of humans band together to capture and detain anything that's not human. Anything that might closely resemble humans but have some ability or physical trait humans does not. A girl with wings would certainly qualify for that.