Cursed

All Alexa ever wanted was to be extraordinary. Instead, she has spent her whole life being anything but and doing anything possible just to survive and protect her younger sister from their abusive mother.
When she is given devastating news that is about to ruin and possibly end her normal life, Alexa learns a horrible family secret . Who she thought is her father, really isn't. Her real father is much more worse than anyone could ever imagine. A result of a centuries old curse gone wrong, he has returned to her hometown, dead set on using her to break this curse.
Now Alexa has until her birthday before this curse takes her over. On the plus side, she is given a chance to be extraordinary, to cure her health problems, but at what cost? Her father wants her dead, her best friend isn't who he says he is and her sister is acting out at learning Alexa isn't her full sister.
What's a girl to do?