Nightbound: Seducing the Vampire Slayer by Ashlyn Mathews

Two houses at war… When an ancient scroll is discovered and the interpretations made public, vampire slayer Phoenix Lancaster refuses to accept she’s the Alpha, her kind’s hope for survival. Or that her family’s hated enemy, Zane O’Day, is the Omega, a vampire destined to love her and with her death, rule over all vampires.