My daughter, who loves to dress herself, will often wear something that does not resemble an outfit. For example: bikini bottoms on top of a leotard. I often remind her that she is not Beyonce and unless you are Beyonce you have to wear pants.
It's been a household rule that has come in quite handy and one that is used surprisingly often. Boom! Parenting win! Until your daughter ask strangers, wearing very short shorts, if they are Beyonce, because they aren't wearing proper pants.