There is a huge difference between being a villain or depicting someone as totally bonkers, and being one-note. Laurie found so many shades of crazy to play in her character, I mean, Jack Nicholson gave one of his great performances in THE SHINING where he was completely crazy, same with Glenn Close in FATAL ATTRACTION. These are villains and pretty nuts ones, but at no point would I describe their performances as one-note. They are wonderful performances that take huge risks by not attempting to appeal to the audience's sympathy in an obvious way.
The problem with this preview (I have no clue what the movie will be like so maybe it's just a marketing thing) is that they are trying to make Margaret a misunderstood mom who deep inside just loves her daughter like the good woman she is. That is possibly the most boring and safe interpretation of the role I've ever heard. It's simply not Margaret, read the novel, read King's comments about the character. Marin Mazzie's "And Eve Was Weak," for example, manages to get us to understand Margaret's actions without humanizing her in the most simplistic of ways.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"