Showing Blood of the Fey (Morgana Trilogy) (Volume 1) by Alessa Ellefson

Morgan Pendragon just wants a normal life. But on her last year at a Swiss boarding school, one of her classmates is found mysteriously dead. Before she knows it, Morgan's called home to Wisconsin, for the first time in her life. There, not only does she have to deal with her crazy-weird family, but she's forced to attend a strange school set in a magical world under Lake Winnebago. To make matters worse, she must train with the others to become Knights of the Round Table and fight in a secret, millennia-old war against the Fey--fallen angels with unimaginable powers who'd do anything to destroy humans. And if that wasn't enough, she must do the impossible: learn to make friends. As the world is falling apart, Morgan must adapt to her new reality before she either goes nuts... or finds herself dead.