Here's an interersting article on Shelley Duvall's Wendy performance:
Source:
vulture.comIronically, according to the novel, Jack Torrance never abused Wendy until he was possessed by the evil of the Overlook Hotel. And she took one hell of a beating in the novel, as opposed to the film version of Wendy, who other than being scared s**tless, emerged largely unscathed from the entire ordeal.
https://www.shmoop.com/shining-stephen-king/wendy-torrance.htmlThat's why the novel didn't work for Kubrick's version I suppose. Apparently Jack already abused Wendy long before, which the article is trying to explain Duvall's performance of Wendy.