Half Sick of Shadows by Laura Sebastian

Everyone knows the legend. Of Arthur, destined to be a king. Of the beautiful Guinevere, who will betray him with his most loyal knight, Lancelot. Of the bitter sorceress, Morgana, who will turn against them all. But Elaine alone carries the burden of knowing what is to come–for Elaine of Shalott is cursed to see the future.

On the mystical isle of Avalon, Elaine runs free and learns of the ancient prophecies surrounding her and her friends–countless possibilities, almost all of them tragic.

When their future comes to claim them, Elaine, Guinevere, Lancelot, and Morgana accompany Arthur to take his throne in stifling Camelot, where magic is outlawed, the rules of society chain them, and enemies are everywhere. Yet the most dangerous threats may come from within their own circle.

As visions are fulfilled and an inevitable fate closes in, Elaine must decide how far she will go to change fate–and what she is willing to sacrifice along the way.