There is a fine line between sexy and trashy...a few women I've dated cross that line repeatedly. Some of the women's dress they wear have all this shiny, sequin stuff and they are too light and skimpy. What's with shiny and skimp on women that are otherwise intelligent and dignified?
It's probably the only way they know how to let loose. If you're seriously dating, just point out some clothes that you like and say something like, "this would look really good on you." If you aren't serious, then don't worry about what she's wearing. :)