Blue Rose — Lola Stvil

This young angel is determined to save the demon she loves… even at the cost of her soul.

Fourteen-year-old Pryor is the leader of a team of powerful angels called the Noru. She's been trained to deal with demons and is always prepared to handle evil. But falling in love with her hot teammate Aaden, she wasn't prepared for that. She's afraid he won't return her feelings and so she runs away to New York City where she dreams of a drama free life.

However, that dream is shattered on a silent summer night, just like the bodies of dozens of humans who suddenly climbed up to the city rooftops… and jumped.

Pryor discovers that there's a new evil in town; an evil that's connected directly to her.  Pryor gathers her team for a mission: put an end to the new evil.

But when the team assembles, she's shocked to find that Aaden is no longer the kind angel she fell in love with. He became a ruthless killer she barely recognizes. Does she have what it takes to save both the mission and her love?

The Noru series in order: 
Book 1: Blue Rose 
Book 2: Last Akon 
Book 3: Fall Of The Chosen
Book 4: When Angels Break 
Book 5: Ways of The Wicked
Book 6: Rise Of The Alago
Book 7: Rage Of Angels