The Isle In The Silver Sea by Tasha Suri

In an England fuelled by stories, the knight and the witch are fated to fall in love and doom each other over and over, the same tale retold over hundreds of lifetimes. Simran is a witch of the woods. Vina is a knight of the Queen's court. When the two women begin to fall for each other, how can they surrender to their desires, when to give in is to destroy each other? As they seek a way to break the cycle, a mysterious assassin begins targeting tales like theirs. To survive, the two will need to write a story stronger than the one that fate has given to them. But what tale is stronger than The Knight and the Witch?