Maybe you could call the style something like post-punk quasi-daring exposure of her underwear?
I would definitely avoid wearing one's underwear on the outside.Wearing one's underpants on the outside means looking or acting like Superman, or trying to do so. Superman wears his red underpants outside his blue one-piece. http://metropolisplus.com/Superman/Superman06.jpg
The well known cartoonist Steve Bell from the Guardian newspaper used to portray former Prime Minister John Major as wearing his underpants on the outside. John Major succeeded Margaret Thatcher as Prime Minister, and came across as very drab in comparison. http://www.artthrob.co.za/03nov/images/bell01a.jpg