Hearing Red by Nicole Maser

In a world overrun by an unprecedented outbreak, two young women find themselves on opposite sides of the struggle for survival.
Saff, a determined new doctor in the first year of her internship, had clawed her way out of a tumultuous past, only to be dragged back into it when the zombie outbreak hits. Forced to join her estranged father and his band of raiders, she’s confronted with the harsh reality that desperation can make monsters out of anyone—even her.
Maddie, on the other hand, lived a surprisingly easy life after the zombies first appeared, safe behind the walls of the community at her parent’s lake house. That is, until they’re attacked, and she’s ripped away from everything she’s known. Now, she’ll do anything to make it back to her family.

And when Saff’s father dies, she finally has the chance she’s been waiting for. The chance to escape. But only if she can steal the medication she desperately needs and survive long enough to get to safety.
With both girls fighting their way to stay alive day by day, in a world where every circumstance is against them, they realize that maybe travelling together can help them both get what they need.
But Maddie doesn’t know Saff’s secret. She doesn’t know where she came from—what she was. And Saff will do anything, especially lie, to get the medication she needs.
The absolute last thing she needs is to fall for some smart ass rich girl who will get in the way of that.