reviled by the public?

The film really decided to focus on the more positive aspects of her character, presumably because they only had so much time.

Georgiana was a great and remarkable woman but she was very, very flawed and the movie barely goes into any of her issues. There aren't any significant scenes about her out of control gambling addiction. She basically threw away the equivalent of millions at the gaming tables (she and friends like the Prince of Wales could easily play for days at a stretch), was never able to sort out her financial affairs, and was heavily in debt till the day she died.

They don't mention the drugs or the eating disorder or the seemingly endless round of parties. They don't mention the other affairs--she likely had affairs with the Duke of Dorset (as did Bess) and Charles Fox and had other close admirers.

They don't mention her tense relationship with some of her in-laws particularly her brother's wife Lavinia and her sister in law Lady George Cavendish. (Lady George hoped that Georgiana would never have a son so that her husband Lord George Cavendish would inherit the estate.) They also completely eliminate the character of her sister Harriet. While Georgiana loved her sister very much she also knowingly helped usher Harriet into the same sort of irresponsible lifestyle and consequently felt honor bound to take responsibility for Harriet's debts as well as her own.

Lots of stuff that they didn't go into. I'd love to see a miniseries about the Devonshire House Set at some point.

Georgiana and Marie-Antoinette were actually friends. Marie actually wrote a letter to the Dutchess (albeit in very broken English).

There are parallels, but I think many differences. Marie-Antoinette was a victim of the times. She was the perfect scapegoat, and almost nothing of what the libelles said about her was true.