In 'The Vampire Diaries', Nina Dobrev spent years playing not only the major part of Elena Gilbert, but also Katherine Pierce, Amara, and several other smaller roles across the course of the many years she was in the show. She finally left in 2015, presumably having decided that the strain of playing so many roles at once was no longer sustainable. She should have just given Victoria Justice a call. Justice could have stepped in to cover at least one of the parts for her, and nobody would have noticed. OK, maybe they'd have noticed the accent change. But you can cover that in the edit, right?
Justice would probably have been all for working in collaboration with Dobrev, too. She's an outspoken charity campaigner and activist, who has spoken in the past about the importance of women working together; appearing as an artist on the 'Unite for Girls' tour which traveled across the United States in 2010.