I now think Mona is AD. She was the original A. Charlotte stole the game from her. It would bring the story full circle if Mona stole it back. Mona is super smart and able to manipulate others. Mona is AD...I think.
And she stayed back in 610 to hear the rest of Charlotte’s story. It shows how pissed (maybe?) she was and she wanted to hear the rest of this thief’s story.
In terms of the story, it absolutely does make sense for Mona to want her game back. But in terms of what a good writer would do - I just can’t see them recycling stories like that. Three A’s, three different people in my mind, and hopefully Marlene’s mind too. Mona being AD, whilst it would make sense, just wouldn’t get a huge reaction from the fans and it most definitely wouldn’t explain Joseph’s statement of “we wanted to give a big reveal and take one last bow” (or something like that). Again it makes sense in the story, but I can’t see it happening anymore.