Mommy, what's wrong?

Annabelle a 28 year old woman, who enjoys living alone, writing books and songs and sometimes doing some dirty jobs so she would be able to survive the month. She's pretty normal, if having imaginary friends and being able to read people very easily was the definition of normal.
But one day, Annabelle gets a strange note, quoting her books. Later on, people from her high school start going missing and are found dead near her home. She keeps getting more and more notes, but has no idea what they mean.
It's obvious that the killer has targeted her, but what does he want?