Frost Walker

Here is the actual summary/description:
Frost's grandfather hired her uncle (the only 2 relatives she has left). They killed her father and now they want to kill her. They realize that the trauma could lead her to kill herself and that's not what they want since they want to do it themselves. Hence, they hire a random kid, Jake from foster care who is a year older than Frost (so he is 17) to befriend her and cheer her up a bit. So they can get closer to Frost and get more information but then he falls in love with her and he breaks off all contact with Frost's grandfather and uncle which angers them and earns him a spot on their hit list.