I'm guessing you mean underwear not inner wear. But I guess it wouldn't matter to me? Like if it was a hot, sunny day and she wore a tank top with her bra showing it wouldn't matter since its hot and nobody likes wearing baggy clothes. But I wouldn't understand why a girl would want to show off her panties. Unless she hoped a guy would spy them and it would give them satisfaction knowing someone acknowledged it?
Personally I think it's awesome. Very sexy, and if the girl enjoys it more power to her. When I see a chick flashing her underwear it's immediately arousing, if you're having fun find some cute guys and put on a show, I'm sure they'll be more than happy to peek.