On screen, part of the present-day storyline is occupied with Violet Bridgerton's slow and uncomfortable realisation that she again longs for romance and intimacy, something she thought she'd never have again after the death of her husband, Edmund. She confides about it to Lady Danbury, who in turn shares stories of her own, terrible marriage and the freedom of her widowhood.
In the book, however, this entire storyline is completely gone from the story. The only present-day scenes are the bookends featuring Charlotte and George, and young Violet has no role at all in the past timeline. In fact, the entire timeline of the book and the show are a bit muddled. The book explicitly says its present-day scenes (and therefore the main portion of "Bridgerton") take place 56 years after the flashbacks. If that's the case, then Lady Danbury and the queen, among others, should be at least in their 70s in the "present" day, but the show does not depict them as being quite that old.