Ravelling Wrath by Eli Dupree

Rinn Akatura has never really cared about the gods, any more than she cares about "obeying school rules" or "being nice to jerks". But when she – and her girlfriend Yali – are chosen to represent the gods in the Ravelling, they get caught up in a decades-old conflict they could never have imagined. In the magical Otherworld, the Blood God enters Rinn's mind and turns her very emotions into a battlefield, leaving her torn between her love for Yali and an ancient enmity that almost brings them both to the brink of death. Can she find a new kind of strength before the Blood God's wrath consumes her?