The Brilliant Death - Amy Rose Capetta

Teodora di Sangro is used to hiding her magical ability to transform enemies into music boxes and mirrors. Nobody knows she's a strega-and she aims to keep it that way.

The she meets Cielo-and everything changes.

A strega who can switch outward form as effortlessly as turning a page in a book, Cielo shows Teodora what her life could be like if she masters the power she's been keeping secret. And not a moment too soon:
the ruler of Vinalia has poisoned the patriarchs of the country's five controlling families, including Teodora's father, and demands that each family send a son to the palace.

If she wants to save her family, Teodora must travel to the capital-not disguised as a boy, but transformed into one. But the road to the capital, and to bridling her powers, is full of enemies and complications, including the one she least expects: falling in love.