Born into Darkness by Mila Young

Three ferocious panther shifters. One broken woman with dangerous powers. A kingdom menaced by evil.
Framed for her father’s murder and facing execution, Snow has lost everything she ever loved, leaving her heart fractured beyond repair. To the point that touch and any emotional connection is unbearable. Seizing an opportunity, she flees the months of cruelty for the safety of the mountains.
But her power-hungry stepmother dispatches hunters, bound by magical collars that turn them into blood thirsty beasts, to kill Snow. If the hunters don’t deliver her heart to the evil queen within seven days, the collars will strangle them, along with any hope Snow has of defeating the witch. What was once a straightforward assassination becomes a devastating attack on her heart.
Betrayal, conviction and revenge collide in this spellbinding romance.