So not dead

What would you do if you saw your dead best friend at your new school? Would you cry,jump for joy,start all over, be afraid. All of the above?
What would you do if that friend had a terrible secret? Run,tell,or just give her what she wants. You'd probably give her what she wanted right? But what if that was your death? What if you had to sacrifice your soul to be her friend? Is she really just a friend in need or something entirely different. Something evil.