Becoming the Queen -- Twilight

Marianna Helen Swan is the half-sister of Isabelle Swan from Charlie's girlfriend in highschool. When her sister came back to Forks, she was the one who supported her obsession with Edward Cullen. Her blind loyalty struck her down however, when Alice and Edward used her as a distraction for Victoria which ended her life.

As luck may have it, she's sent back in time by the Goddess of the Moon right before Bella comes to Forks. Now, she has one objective in mind: Protect her sister from the Cullens and exact her revenge on Edward and Alice. How does she do that, you ask? Well, by becoming the Queen of Vampires obviously.