This here's a 2-for-1 special, considering that the yellow paper ward on Hsien-Ko's hat is actually her twin sister, Mei-Ling. Their mother lost her life protecting her daughters from evil spirits, her soul being lost in darkness as a result. Wanting to save their mother's soul, the teenage girls cast a forbidden spell which turned Hsien-Ko into a jiang-shi (Chinese hopping vampire/zombie) and gave her tremendous power.
As for Mei-Ling, she takes the form of a paper ward to prevent Hsien-Ko from losing control of her new powers. This enables the sisters to fight as one being, as they combat the evil that took their mother from them. It's a pretty insane take on the power of the bond between twins.
It's worth noting that Hsien-Ko has giant claws chained to her body, and tons of other weapons hidden on her person at all times. She's basically a blue-skinned iron maiden.