Nina Dobrev
Nina DobrevReuters

Nina Dobrev's return to The Vampire Diaries is still shrouded in mystery and the actress has refused to put to rest rumours of her comeback by saying she was not allowed to talk about it.

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During a visit to AOL BUILD Series, Dobrev was once again asked about reprising her role as Elena Gilbert, but she refused to reveal her character's fate, saying: "I haven't ever told secrets in the past and I'm definitely not going to start now.

"Sorry, guys, I'm not allowed to talk about that," Dobrev said with a smile.

Dobrev quit the vampire drama after Season 6 to pursue other acting projects. Following her departure, the writers did not kill off Dobrev's Elena but chose to keep her in a magic-induced sleep from which she'll wake up only after Bonnie's death.

Shortly after Dobrev's departure, The Vampire Diaries showrunner Julie Plec revealed that Dobrev has promised to return to the show to wrap up Elena's storyline. "I feel very good about it!" Plec told Entertainment Tonight when asked about getting Dobrev back. "She and I have spoken and I know that she 100 per cent wants to be there and I, of course, 100 per cent want her to be there, and so it just comes down to stupid things like scheduling. Honestly, let's put it this way: I would be devastated if it weren't to work out, so I have a feeling the cards will be in all our favor."

Plec also opened up about her vision for the series finale, hinting it will be a happy ending with a touch of tragedy. "Our show is supernatural, so sometimes closure means death and tragedy and sad endings -- which can be just as potent and powerful as happy endings -- so I have to imagine that we'll have a mixture of both," Plec said.

The Vampire Diaries is aired on Fridays on CW.