It's one frame only, where her dress rises as she throws her arms up.
During the large-scale and racy Carioca dance sequences, and in the memorable Flying Down to Rio number atop bi-plane wings, skimpily-attired chorus girls performed wing-dancing and other stunts the sequence was filmed in an airplane hangar with wind machines and a few planes hanging from the ceiling - enhanced with backdrops of Rio and Malibu Beach.
At this point, my female readers can click to another site unless you can enjoy the niceties of the female form, in which case, please send me photos of your favorite female form.
There's a lot of big sharks in here that just live on fresh fish like you.