I'll write this out more comprehensively, but I wanted to give a quick lost of backstory beats to make sure it meshes with what the gm and other players have in mind. 

1) born on earth, but raised on Azarath for the majority of her childhood. 

2) banished after an incident made the monks of Azarath realize how dangerous the daughter of their greatest enemy was to have around. Came to earth around the age of 12. 

3) found by authorities, and placed in foster care, from which she ran away to find others like herself. Joined the Titans, and learned to fight and further control her powers. 

4) Trigon attempted to enact his plans for her, but with the help of the Titans, he was bound in the void between worlds. 

5) Raven returned to Azarath to keep watch over her father. 

6) ignores a premonition of great doom until after she heard the news of Superman's death. 

7) returns to earth to help restore the world that first made her feel at home