What is the main conflict in Blood and Chocolate by Annette Curtis Klause?

Vivian is a werewolf living with her mother and her pack in a city in Maryland. She falls in love with a human boy, but is devastated when he is unable to accept her for who she is. Her rage and grief cause her to lose control of herself while in wolf form. When murders begin to happen, Vivian is terrified that she is the killer. However, she learns that another werewolf in her pack, Astrid, has been setting her up. Astrid now plans to murder Aiden, so Vivian runs to his defense, only to find that Aiden means to kill her.