The Throne of Broken Gods by Amber V. Nicole

"Then, Samkiel, you will know this is how the world ends." But it was not this world. No, it was mine. It was Dianna. The world quakes in fear as the last shred of Dianna's humanity is ripped from her. As it should. Grief consumes Dianna, burning away any semblance of good within her and threatening the budding relationship between her and Liam. Now, Liam must pull her back from the brink of complete damnation before time runs out.