I Am Number Four question

I am looking for a book that I read on Amazon Kindle. It was about a girl who was orphaned after a big magic world. She lives in the woods with her mentor who taught her to be a warrior. I believe his name was Matthews. Her best friend was a green forest spirit that looks like a deer. I believe his name was Enzo or something close to that. There is an academy at that all the soldiers attend and certain magic is outlawed after the war. On her 18th birthday, she goes to a grove of special trees that are full of magic. Before she is able to talk to the trees, a solider named Winston kneels before them. They do not talk to him. When she approaches, 3 or 4 of the trees light up and talk to her. A bunch of stuff happens but she falls in love with 4 guys who are soldiers. One is half wraith. He takes her to the part of the village all the wraiths live in. At one point in the story, there is a battle outside of the wall around town by the forest she lives in. She reveals her powers. All the men stick beside her. Toward the end of the book, she goes into the basement of the academy with Matthews. The EVIL headmistress puts her in a box and tries to suck out her magic. All of the guys are chained to the walls. They escape. Matthews dies protecting her. She goes back to the trees. All 7 light up and give her a prophecy. I CAN NOT remember the name of this book nor can I find it in any of my reading history! Please HELP!