Theory about Cassandra and Ginny
Obviously they were really good friends. So here are two theories:
1. Cassandra played a part in removing Ginny from Alex's life because they really needed him. SO they staged her death and hiding her somewhere.
2. Ginny is part of the group so she came back and played Alex, because they needed him to be a player.
Either way it seems like Cassandra is obsessed with Alex or something, why would she care about him so much, after all she did try to encourage him by telling him "be good." looks like something will happen between them since Ginny is out of the way. Maybe he will be mad at Ginny for playing him or she will be really killed during the season.