The Trouble with Death and Demon Gods - Cary Redmond, #7

Trouble's Last Stand. Magical Protector Cary Redmond has not been enjoying her test year. Discovering she absorbs magic, figuring out how to release that magic, and dealing with enemies from her past regularly complicates her life. Her seventh year has been overflowing with Trouble. And way too many demons and vampires. Now, with only two months left to go, Cary must face her greatest enemy again.
Not to stop him. But to protect him. Family squabbles suck. And when they involve demons, chances of realm destruction are high. Cary will need all the help she can get in this epic stand against the forces of evil. Because if she can't stop the demons this time. Her world will burn.