Heart Of The Mirage: Book One of The Mirage Makers by Glenda Larke
Stolen from her people as a child and raised as a citizen of the Tyranian Empire, Ligea Gayed is the obvious choice to despatch to her homeland, occupied Kardiastan, with orders to root out a rebel conspiracy.
At first, she devotes herself to her new assignment with zeal. Adopted daughter of the Empire's greatest general, and possessing a fearsome reputation within the ruthless Imperial spy network known as the Brotherhood, Ligea views herself as a loyal servant of Tyrans. But blood will out, and with each day she spends among her parents' people, her disciplined self-image crumbles a little.
And there are secrets in Kardiastan, secrets that will inevitably force Ligea to choose between her upbringing and her birthright. Secrets that will shape the destiny of two nations. . .