The Emmanuels (both of them wrote the book) described her as wonderful and down to earth. At one point he was meeting with Diana at Buckingham Palace and the two of them went out on the balcony and waved at people.
The Emmanuels spent a lot of time researching past royal wedding dresses and considering the scale of the venue. They actually went to St Paul's to measure the aisle.
Some of the lace on the bodice came from the collection of the Royal School of Needlepoint. Queen Mary (Grandmother of the Queen Elizabeth) had donated it during WW2 for a fundraising program.
This is the book:
https://www.amazon.com/Dress-Diana-David-Emanuel/dp/0062088033