I think there were plenty of young gals wearing flip flops. They are in style. The wearing of flip flops caused quite a controversy at the "other" DC not that long ago. WASHINGTON DC, that is.
http://usatoday30.usatoday.com/news/offbeat/2005-07-19-flip-flops_x.htm
I guess I wouldn't be surprised if they institute a new rule about flip flops just like the unwritten rule about beards (at least in the US).
Doc