Secrets of Jin-Shei by Alma Alexander

Enter an ancient world of courtly elegance and intrigue, where sages are also sorcerers, and the daughter of a lowly seamstress can become a companion to an empress. In this magical land there is a secret language -- a language that women have passed down from mother to daughter for countless generations -- a language that signals a bond like no other ... the bond of jin-shei.

Set in a mythical Chinese kingdom, The Secrets of Jin-shei is a timeless story of what sustains friendship -- and what tears it apart. Accepting all the joys and responsibilities of jin-shei, eight girls pledge lifelong loyalty to each other: the poet, Tai, whose promise to a dying girl changes the history of an empire; the warrior, Xaforn, an orphan who will protect her chosen family no matter what the cost; Khailin, the scholar, whose thirst for knowledge leads her into a world of dark secrets and alchemy; sage Nhia, the only person with the power to save Khailin; Tammary, the gypsy girl, whose secret lineage could ruin a royal house; Qiaan, daughter of a captain in the Imperial Guard, with family secrets of her own; the healer, Yuet, confidante to the empress; and the empress herself, Liudan, whose search for family and ultimate quest for immortality holds the power to destroy them all.