The Sun and the Void (The Warring Gods #1)

"When Reina arrives at Aguila Manor, her heart stolen from her chest, she's on the verge of death--until her estranged grandmother, a dark sorceress in the Don's employ, intervenes. Indebted to a woman she never knew, and smitten with the upper-caste daughter of the house, Celeste, Reina will do anything to earn--and keep--the family's favor, even the bidding of the ancient god who speaks to her from the Manor's foundations. To save the woman she loves, Reina will have to defy the gods themselves, and become something she never could have imagined"--