She's wearing a Ryukyu bingata kimono and posing for the Yotsudake dance. Yotsudake is one of Okinawa's most beautiful and elegant dances.
"Bingata" literally translates as "red stencil." However, a variety of colors are used in bingata kimono. The art of making bingata kimono almost died during World War II when many of the treasured bingata stencils were destroyed. Fortunately, a handful of bingata artists (at least one is a Living National Treasure) have continued to revive the art.