Ya..I just made a post about this..basically it was supposed to be Wren as AD but they needed someone they could guarantee to come back..Jullien was too busy ..so they needed AD to be a series regular. And having one of the liars as AD was never an option.

Ya I also heard in the book all had a twin. Like the story she told her friends about where the twin stabbed her own sister..if I remember correctly that was about her and her sister.