Belle has dark skin, dark brown hair tied into a ponytail with a pink bow supporting it, and also has braces like Luan. She wears white pearl earrings, a white long sleeved shirt, a pink sweater tied around her shoulders, tan cargo shorts, white socks worn up high, and black and white shoes.
Like Luna, she plays musical instruments, but she plays classical instruments rather than rock 'n' roll instruments.
Coincidentally, they're both voiced by Mariana Torres in the Brazilian dub.
Her name comes from the word belle, which means "Beautiful" in French.
Her brother's name "Beau" is the masculine form of the feminine word "Belle" in French.