Alternation Complete Saga by Anthony Marino
Alternation Complete Saga: Ember is Erica's older sister a girl who battles demons, coming to her rescue is a protector from another realm, but the demons who are actually aliens will not leave without her essence. She battles on courageously, while the demons play with her mind. If you know anything about the plight of the Pearls, you know you’ve got to avoid the heat. Ember’s sister Erica received some gifts for her birthday, which changed her little life forever; the gifts changed her into a wolf, other people, etc, and opened portals to other realms within her mind. If she doesn’t get a handle on these things, she may find that she’s faced with an apocalypse and possibly her end.