The peplos is an exaggerated Spartan-style peplos, with side slits. This is worn to give a pelvic curtain or a 'tabard'-like appearance. Most fan artists will not depict the peplos. Instead Mercy's upper garments will be merged into a single chiton 'dress', with the brooch-pins being purely vestigial. Such cases should not be tagged peplos.
The crotch flap and other dangly cloth bits may often be depicted as wrapped around her other clothes. Tagging himation would be appropriate then.
