'The Vampire Diaries' star Kat Graham will play Motown star Tammi Terrell in an indie biopic set to shoot next year. Tammi Terrell's story is finally getting the big-screen treatment. The Motown singer will be portrayed by Kat Graham of "Vampire Diaries.". 'Vampire Diaries' star Kat Graham will play late singer Tammi Terrell in an upcoming biopic that says Graham. “Tammi Terrell defined passion and soul itself.