Looking for a young adult novel, gemstones for eyes

I’m in search of a single young adult novel in which the main character is a young woman, she’s been training in an academy of girls, learning how to fight (and possibly use magic?) She comes of age and there is a ceremony where her eyes are replaced with gemstones, I believe they were obsidian but amber or garnet are also sticking out in my mind. She goes on a journey where she meets a man (and later there is a romance between them). They are on a boat at one point, she senses a monster or wizard and uses magic to defeat them. At the end of the book she uses the power of her gemstone eyes to speak to a council of people about something important, then can’t turn off the power and it slowly drives her mad. A former witch (sorceress?) finds her and manages to remove the stones and gives her blue eyes. I think one of the names starts with an s, could be wrong. I read this around 2015, the cover was, I believe, a young woman with gemstone eyes. Perhaps a golden background.
Any and all help is greatly appreciated!!