Stylistically, isn't it possible that Grayson & the DS directors were simply attempting to capture, on some level, the heightened acting style found in the classic Universal horror pictures and other early horror films? I don't feel Grayson was trying to be campy. She was playing it "big" but not for laughs.
Unfortunately, the grand stage actors of yesteryear would be considered "hams" if they tried to make a movie or TV show nowadays, but this stylized form of performance seems well-suited to classic "spooky" movies and shows when done well. It can come off sort of goofy when pushed TOO far though. For example, I think Tod Slaughter (old-time British actor) is loads of fun, but man that guy just goes WAY over the top sometimes.