Spoilers for SPN 4x01 Lazarus Rising
So I gave the whole Ruby thing some thinking.
When Christy/Ruby opens the door, she doesn't really look shocked to see Dean and when Sam grabbed his knife and attacked Dean, she lets out a little scream, which suggests either she's a wonderful actress or she isn't Ruby yet. But later in the diner Ruby (in Christy's form) and Sam are talking and he said something like 'What WE are doing' which suggests that they have been working together for awhile. So, does Ruby constantly change her meat form or is she good at hiding her shock of seeing Dean? (Maybe she already knew Dean was back, or something.) What do you think?