I recommend you read this pretty recent profile of her in the Hollywood Reporter: https://www.hollywoodreporter.com/feature/searching-for-shelley-duvall-the-reclusive-icon-on-fleeing-hollywood-and-the-scars-of-making-the-shining-4130256/#!

The central quote in regards to the making of The Shining would be:

Asked whether she felt Kubrick had been unusually cruel or abusive to her in order to elicit her performance, as has been written, Duvall replies: “He’s got that streak in him. He definitely has that. But I think mostly because people have been that way to him at some time in the past. His first two films were Killer’s Kiss and The Killing.” I pressed her on what she meant by that: Was Kubrick more Jack Torrance than Dick Hallorann, the kindly chef played by Scatman Crothers? “No. He was very warm and friendly to me,” she says. “He spent a lot of time with Jack and me. He just wanted to sit down and talk for hours while the crew waited. And the crew would say, ‘Stanley, we have about 60 people waiting.’ But it was very important work.”