I'll start adding all those who asked now.
And IKR? ^ was wondering that, he's been talking to her since the beginning and then last episode we got a full blown interaction. I think he had something to do with her concealment
Also a couple of use discussed a couple of months ago that the reason why Mary feels connected is because they're related. I picked up on Clarissa sounding like Mary a few weeks back and a lot of people agreed. When she screamed it sounded just like Mary.
As for the ghost, I thought she wasn't real, especially with the hand on the screen. Oh and that little girl saying a ghost was at the French Court, but then as episodes went on I came to realize she was real.