White wonder

If you were going somewhere very public with a friend and she showed up wearing a white sun dress with a white bra and a white thong and you could totally see her ass, do you see if as your duty to tell her? Or would it be more a courtesy thing if you decided to say something?

OR

Would you totally let her walk around a public park all day with the sun shinning brightly and her ass in plan view for all to see, because, hey it's her ass and she's gotta know white over white isn't a good thing...?