The Captain’s Door by C.S. Houghton

At the helm of a tall-ship stands Mina Paradis, indentured by contract to a corrupt world of 19th century espionage and fantastic devices. She may look young, but she’s spent a lifetime serving the secretary of New England, her mother.

Trapped in a body that still looks ten, Mina uses her appearance to slip past enemy defenses. It used to feel like a game, but now she hardly sleeps and the panic attacks are getting worse. She’s tired, so tired of watching her friends grow old and die while she sails the world observing and murdering her mother’s political rivals.