A really interesting show, that depict the conditions of (white) women a few centuries ago and the behaviour of (white) men toward them. I really enjoyed the pace and the mystery that surrounds the main character.
[spoiler] I think something that the show did well is show the behaviour of men. Except for Jeremiah, all the men are guilty of something and they all want something out of her/only see her like they want to. Even the doctor, who don't have any bad intentions toward Grace ends up hurting another woman. I also believe that Jamie said she was guilty during the trial because he saw she wasn't truly interested in him and was "avenging" himself and this is why she can't forgive him in the end. He also puts her in a very awful position after they're married as he forces her to recall traumatic events just... before having sex with her...
Anyway, the most logical conclusion for me is that she suffers of some kind of traumatic disorder and thinks of herself as Mary when she commits acts that might be reprehensible. Mary was such an important figure for her that Grace has lived her entire life wanting to accomplish Mary's dreams. She was the only person toward whom she could be truly open about things and losing her also meant going back to a situation of loneliness, without anyone to teach her about life and to listen to her. For me, the real trauma is not just the death of Mary but also the fact that she couldn't find another friend. I do wonder if Nancy's death is also linked to her not being the friend Grace thought she would be.[/spoiler]