Guardian Legacy, book 2: BetrayedEdnah Walters2011

Lil isn't just an average teenager. She's one of the Nephilim--the descendants of humans and angels--which gives her some serious psi skills and a mission for redemption. Just when Lil thinks she's found a balance between her normal life with human friends and her training to become a Guardian, she's warned that someone close to her will betray her. When the boy she loves starts acting strangely and one of her human friends acquires a supernatural ability, Lil begins to realize that someone is manipulating the people she loves... and won't stop until she's been lured to the dark side.