Speaking to the New York Post, Graham praised the recent storylines examining the way Bonnie's magic has affected her health.
"They're definitely playing with Bonnie's mortality a lot, which I love," she said. "It wouldn't be a great story if everything worked out perfect and everyone was safe whenever she did a spell."
She continued: "You have to show a character's weaknesses for people to identify with them. I never saw Bonnie as an all-powerful, indestructible person. Even though she has all this inner strength, I see her as this little girl who got caught in the middle. I kind of want to keep her vulnerable so we find her strength from that place instead."
Graham, who admitted that she is prepared for the possibility that Bonnie will die, added that her magic will continue to be a theme in future episodes.
"Let me tell you, it's about to get crazier for her in terms of her powers," she said. "It doesn't lighten up. It shocked me. And that's all I can say."
The Vampire Diaries airs on Thursdays at 8/7c on The CW in the US. The second season returns in the UK on February 1 at 9pm on ITV2.