This isn't just some lady. It's Yuka Saito.
As a third-year student at Gakushuin University, she was awarded a prize at the Miss Campus Queen pageant. She also models for Japanese fashion magazine CanCam. Here she is in Akihabara.
See how she stacks up to her 2D counterpart!
劇場版ブレイクブレイドのコスプレイヤーさん 「美人っすな！」「短パンとふともも！」 - アキバBlog [Akiba Blog]