The Prison Healer by Lynette Noni

Seventeen-year-old Kiva Meridan is a survivor. 

For ten years, she has worked as the healer in the notorious death prison, Zalindov, making herself indispensable.

Kept afloat by messages of hope from her family, Kiva has one goal and one goal only: stay alive. Then one day the infamous Rebel Queen arrives at the prison on death's door and Kiva receives a new message: Don't let her die. We are coming.