Cosmos from Aku no Tesaki ni Natta node, a manga by group U-Ral.
Afaik, she doesn't have a civilian name. The colors of her civilian form is not official, I just went with what made sense for me.
Description
fbcosmos, magical girl, 1girl, solo, very long hair, single sidelock, mini top hat, hat flower, hat ribbon, hair ornament, green eyes, choker, bare shoulders, strapless shirt, detached sleeves, elbow gloves, neck bow, frilled skirt, back ribbon, bike shorts under skirt, knee boots, high heels,