The Avatar's Guardian: The Lost Story (Avatar the Last Airbender fanfic)

Water, earth, fire, air. The avatar Aang defeated the fire lord. Everyone knows Aang's story, but something or rather someone was left out of: Satomi, the avatar's guardian. The guardian's life is tied to the avatar's life directly, and the guardian can't be a much of guardian if he or she can't fight. So the guardian can bend all four elements and use the avatar state like an avatar. The only downside, of course, is if the avatar is mortally wounded the guardian's life force is drawn on to save the avatar. Satomi wants to severe this tie because unlike the avatar the guardian can not be healed with water bending. The guardian, however, can not replace the avatar. Satomi shouldn't have been born, and she has been shunned her whole life for it.
Follow Satomi's journey alongside Aang and team avatar. Her is past is tied to Aang's, but what will the future hold. Satomi's past is dark, and so is her future unless things change and soon. She battles along side Aang and team avatar, but there is a battle of her own she must fight. A battle that was never told. A fight she has to win or risk losing her avatar and the person she has vowed to protect even though she wants nothing more than to get out of the guardian business. The young teenager struck a cord in her, and she has deemed herself responsible for him ever since.
You'll have to read to discover who this mysterious person is, and to see whether or not Satomi can scrape out with her life not to mention the lives of her friends. And what will happen when her past returns to haunt her? Do the other discover her secrets? The biggest question of all though is what happens to her when she severs the tie? Read to find out.