Speaking to Entertainment Weekly, Graham explained that the couple will team up to help fight the dark forces in Mystic Falls.
"[We're working together for the] greater good, and really getting to be together," she said.
"You'll be able to see a lot of heartbreak between them both. Those characters are [going to] really go through it before the end of the season."
Graham explained that all the characters will work together to protect each other, joking that they are "very similar to the Scooby Doo gang".
She added that Bonnie will "put a lot on the line" to keep Elena (Nina Dobrev) out of danger, explaining: "If it ever comes to having to do something for Elena, Bonnie will go balls out for her. She doesn't care. Klaus coming into the show is going to cause chaos. People are going to have to figure out what these characters have to do to save their lives."
The Vampire Diaries returns for a new episode on April 7 at 8/7c on The CW.