The Life of Cassiopeia Black

Summary: Heather Potter is actually the daughter of Lily and Sirius? Why does everyone think she is James Potter's then? Well, because Dumbledore compelled Lily, James, Sirius and Remus to forget. Now Lily and James are dead and Sirius is in St. Mungo's in a magical coma, so where is Heather? [AU, fem!Harry, Good!Voldie, Bad!Dumble, Light!Bashing]