A challenging question - mulling it over ... I think femininity has less to do with an outfit or physical appearance, and more to do with inherent personality/behavior/attitude.
Following this through, I believe it supports Angie's remarks on how she always feels feminine, even when dressed in a less *traditionally* feminine style. It comes from within. And what we feel within has a way of instinctively informing many aspects of our behavior and thereby the signals we project to the world. It's a sort of aura - for lack of a better term.
Could anyone be more feminine than Audrey Hepburn? Even dressed in pants and a shirt, short hair and with her slender "boyish" figure, she's as girly as they come. Staying within the same era, take Jayne Mansfield. Touted and positioned as a sex goddess, in my opinion there was nothing feminine about her. Despite her hair and figure, her provocative outfits and movie roles, she was not a feminine woman. She exuded sexuality - but not femininity.
Anyhooo, all this rambling in the wee hours is by way of saying: although femininity may be enhanced by one's external appearance, I believe it is an elusive quality that comes from within.