Coven of Lies by C. J. Beaumont

A crumbling partnership. A fickle magic. A vicious killer.

With one witch already dead and her sister missing, Roxy Cole is hellbent on finding the killer stalking the Bayshore coven. But keeping the coven safe and finding the twisted killer is proving more than dangerous, especially when Roxy’s tentative alliance with Ray Hammond is crumbling fast.
Worse than that, Roxy can’t seem to escape her grandmother’s looming prophecy that six more witches are going to die if Roxy keeps searching for Kat. She can’t just let her baby sister go, and is desperate to find a way to beat the odds and see her sister home safe without losing more witches in the process.
She knows only one thing can save them all: her magic. But she turned her back on that path a long time ago, and now—when she needs it most—her magic is playing hard to get. She’ll have to find a way to tap into it, even if it means strengthening the darkness that was born when she made the biggest mistake of her life. If she fails to fully embrace her gifts, she will lose her sister and the other witches to a gruesome death, and she will never be able to live with herself.