Good shot. The relaxed face, poised arm, white beads framing the eyes, good stuff. The only thing missing is the feet. Pow-Wows are a whole body thing. I have never heard this being called a Prairie Dance. Must be an east coast west coast thing. Around here it is called a Grass Dance.
I like the tight cropping because I feel that the movement of the dance is implied by the composition. I felt like showing the entire figure would have pulled away from the detailed nature of the costume and somehow diminished the image.