Adopted Assassin

Warning-
Not great at descriptions, will need help creating ideas for this book, and this is my first book, so please be nice. This is based off of a tumblr post I saw on instagram. There are probably millions of books like this.

Description-
Based off of a tumblr post.
I am an assassin. I am a werewolf. I travel the country killing people who harm the innocents of our nation. I protect the innocent. I am the Dark Phoenix.

What happens when the Dark Phoenix is asked by a little girl with a handful of dollar bills and loose change to kill her abusive father? What happens when this girl is a werewolf? Does she move in with the Dark Phoenix? What is the Dark Phoenix's real name?