Her name is Hatsune Miku. "She" an avatar, is actually a vocaloid, a program that synthesizes human speech to the point that it can sing.
A singing computer program, using holographic technology.
You can clearly see the cyber-anime lass strutting her stuff as she's projected live onto a glass screen.
Hatsume Miku - World is Mine Live in HD
Hatsune Miku is a rising star in Japan and abroad, singing catchy J-pop that matches her blue-green hair. She's also a virtual avatar created by Crypton Media using Yamaha's Vocaloid voice synthesizer. That hasn't stopped her from amassing a legion of fans who really love her work. I mean really love it. Check out the crowd frantically waving glow-sticks and singing along...