Daughter of Persephone by Helen Scott

Poppy is nothing special.
She was making ends meet and trying to enjoy life. But a strange necklace caught her eye at the thrift store. Now, three gorgeous men have stumbled into her life, and she’s torn between being terrified and excited. That is until they tell her she is the future queen of the Underworld.
Not only that, but she needs to bond with her hellhounds, the three heads of Cerberus, and protect the Underworld from a goddess who wants it for herself. Forced to face unnatural enemies, and too-sexy-for-their-own-good men, Poppy must choose: keep the life she’s always had or take her rightful place as queen.
If she survives.