Could someone explain what the A B etc means? Episode 6 has 3 versions @_@
A and B means the 2 parts of an episode. Some sites upload episodes as 1A and 1B, 30 minutes each while others upload it as a whole hour. Regarding your sentence 'episode 6 has 3 versions' that I have no idea.
I think the main nurse just believes that she is MY's mother. This drama is about mental issues so it can be that the nurse has delusion of grandeur. She must have been a fan of DHJ and when DHJ disappeared she started believing that she is her. She could have manipulated POR to help her.