Guardians: the sister and the grandma, book 4

One just became leader of the guardians. She went out for a walk at night but felt a sensation of dangerous. She led herself to a place she thought she'd never go again, the school. She helps a little girl but along the way her and her mom meet up in a fight against the shadows. One figures out something big when at least one word is spoken. One will go through this to find out what she has been missing.