The Path of Thorns: A.G. Slatter

Asher Todd comes to live with the mysterious Morwood family as a governess to their children. Asher knows little about being a governess but she is skilled in botany and herbcraft, and perhaps more than that. And she has secrets of her own, dark and terrible - and Morwood is a house that eats secrets. With a monstrous revenge in mind, Asher plans to make it choke. However, she becomes fond of her charges, of the people of the Tarn, and she begins to wonder if she will be able to execute her plan - and who will suffer most if she does. But as the ghosts of her past become harder to control, Asher realises she has no choice.