There is a ton of literature (and a thread here on the forum) about Wallis, and her social skills/habits are well docuemented as being engaging and gracious. She was definitely not the loud-mouthed drunk as portrayed in the film.
Also, I don't see any reason why hollywood would seek to portray her as tragic, misunderstood, and sympathetic. The film was not about her and the characterization of her in the film elevated the sympathetic view of the film's hero and heroine--Bertie and Elizabeth. Not devastatingly so, but enough to misrepresent Wallis in a way I found unfair and unbecoming of honest film making. That said, it was not a major distraction from the core story; just an annoyance for those of us who don't like seeing her frequently thrown under the bus.