I read a teen novel in high school and I can't remember the title. It was about these teenagers, that I think were like the reincarnation of gods or something. In the end, I think her best friend was her nemesis, and the best friend was trying to kill her and her boyfriend. So, the best friend ground up pieces of glass and cooked them in the food in order to kill her and her boyfriend....The exact details are really fuzzy, cause its been so long since I read it. I do know that the book was part of a supernatural/romance collection.