Question: This is regarding the scene in Boston. Why was that one gal smiling? Why did Amelia turn the lights out? Who were the three men Amelia told "You can go in now?
Answer: The lady smiling is one of Amelia's relatives who sits on the company board of directors. Being as she is elderly, she appears to be somewhat unaware of what exactly is going on and just sits there, apparently amused by the proceedings. The men were just waiting their turn to meet with the board, and of no significance to the story. Amelia's turning off the lights is just an exaggerated comedic gesture to show that she is on her way out and heading to Hawaii, that really makes no sense.
Answer: I think it's her Irish frugality.
Answer: I think Amelia shutting off the lights was meant to imply she is extremely frugal and cautious with money, indicating she would more than likely scrutinize over judgment of her father (Doc Dedham).