Bonnie is Elena's best friend. She finds out that she is a very powerful witch, just like her grandmother, and is also a descendant of Emily (Katherine's witch, who entombed them under the church). Her grandmother is the one who freed the vampires from the tomb, after Damon convinces her. When her grandmother dies, Bonnie leaves town. When she returns, she is distant to Elena. Later you find out it is because of Stefan and Damon, who she believes is responsible for the death of her grandmother. Though she hates all vampires, she helps Stefan and Damon get out of the burning building with a spell in the last episode of Season 1, knowing that if they died, Elena would be very hurt. She later tells Stefan that if Damon spills one more drop of innocent blood, she will kill him and if Stefan gets in her way, she will kill him too.