I finally got around to renting "Saving Mr. Banks" about the collaboration between Walt Disney and P. L. Travers to make Travers' Mary Poppins books into a movie.
The official web site includes video clips, including this one which demonstrates Travers' relentless bitchiness.
Never Ever Just Mary - Saving Mr. Banks Clip on Disney Video
Considering the movie was made by Disney Studios it's no surprise that Walt comes off as a lovable guy - but then, that's why they hired Tom Hanks to play him. They do play fast and loose with the actual sequence of events according to the Wiki about the movie though. But they almost make up for that with a nice little easter egg at the end of the movie - in the main movie Emma Thompson's Travers is shown demanding that her consultation sessions with the Mary Poppins' screenwriter and composers be audio taped, and during the end credits they play an excerpt from the actual Travers taping sessions. Unfortunately that isn't available online as a video clip - you'll have to see the movie.
Travers is portrayed as constantly drinking tea - which really put me in the mood for tea. At one point in the movie her driver, played by Paul Giamatti, gives her tea in a paper cup, which she calls "sacrilege" which I'm inclined to agree with.