Kyou kara Akujo ni Narimasu! Tsukaisute no Migawari Seijo Nante Gomen desu

Princess Leonora is a one-of-a-kind saint with healing powers... Or so she wants people to think, but in reality, she's been secretly making her maid Eda use her miraculous power to heal people, and the overuse of that power has run Eda completely ragged. Even worse, Eda had always loved Leonora like an older sister, but ends up having the princess throwing her into the water and completely abandoning her! Just when Eda thought she was dead for sure, Groh and a group of other soldiers from another empire rescue her and ask her to help them triumph over their enemies as a true saint... Huh?! No way! She's sick of being a saint and a maid! She's going to be a wicked witch and bring the country to ruin! Source: Ichijinsha