Cass, Cassie, Casey, Sandy, Sandra, Andy, Andra.
Famous people named Cassandra:
Model Cassandra Lynn (Hensley); novelist Cassandra Clare; jazz singer Cassandra Wilson; daughter of athlete/TV personality Caitlyn Jenner, Cassandra "Casey" Jenner.
TV presenter Elvira - a.k.a. "Mistress of the Dark" - is actually Cassandra Peterson.