Angel (Book 1) (Many Mansions)

Fifteen-year-old Angel has lived in a mental institution for too long. There's something she must do - perhaps someone special she is destined to be - but she can no longer remember. After a perilous escape, she embarks upon a strange adventure into alternate dimensions of reality with her mysterious friend Selena. After a long journey among the interstices between the worlds she discoves her true identity -- but can she find the courage to accept it?