Cassiopeia Black and the Second Wizarding War

Cassiopeia Black: a Slytherin, and a pure-blood, with an unacceptable crush on a blood-traitor, and a best friend with confusing feelings for her. Raised by the Tonks and the Malfoys, Cassie is torn between two worlds when she is finally forced to make a decision and leave one behind forever. Can she give up what she wants most to save the Wizarding Community, and maybe the world?