Guardian of Eden.

Eden Channing, moves to a new high school after her mother dies in a car accident and then falls in love with Gabriel, a 143 year-old teenage vampire. Students begin dying from what the adults believe to be suicides or drug overdoses, when it is the evil vampire Luscious who is doing them in. Now he has set his fangs for Eden. Gabriel must decide whether to let her die or condemn her to a life of vampire-ism.