From the description:
"Cardinal Richelieu is dead, a victim of poison. The throne of France, which he has long protected, is once more unstable as rival factions vie for power. But the Cardinal has appointed two heirs: one to his religious position, and one to head the elite spy ring that has maintained France's fragile political balance. Francoise Marguerite de Palis, the Cardinal's lovely but low born niece, is devastated by her uncle's murder and vows revenge, which she sets out after immediately. Though the task is daunting, she at least has some formidable tools at her command. Not only is she now the head of the Cardinal's Eyes, but is arguably the most powerful Sorciere in all France. Shapeshifting into her character Biscarrat, notorious swordsman, she sets out to find her uncle's murderer. But with an unexpected ally."
4 stars on a very scant 10 reviews, with 2 of those being one star, so you are taking a chance here. 369 pages