Here's what an author of a Travers biography - someone who actually talked with Travers - had to say about Travers' reaction to the Mary Poppins movie:
And in the beginning, she was quite praising of the film, because she believed there was going to be a sequel. But Disney died in 1966, so that didn't happen. And as time went on, she got more and more annoyed with the film, and disliked it more and more, for being false to what she had created.
http://articles.chicagotribune.com/...0131220_1_saving-mr-p-l-travers-p-l-travers/2
So I'm betting that the scene at the end of "Banks", where Travers found herself liking the film, but denying it because of pride, is at least partially true. She was probably already ticked because she hadn't been invited to the premiere - and doubtless she knew why - and then to find herself liking something she was prepared to loathe, and worse, crying over the songs - a theory stipulated by "Banks" director John Lee Hancock - well, that must have been unbearable. Afterward she recovered and told Walt "We still have a lot of work to do" (can you imagine? The film is obviously done, it had gotten a standing ovation by the audience at Grauman's Chinese Theater, and she thinks the film should and can be changed - what planet was she living on? Planet Ego?) and of course he told her "Pamela, that ship has sailed". That no doubt ed her off, because she was, as you say, a mentally disturbed woman. She got worse as she got older, no doubt, and that's when the bitterness over the film truly emerged. Well, nuts to her. She never knew how extremely fortunate she was when Walt took an interest in her book, and that was HER loss and our gain.
