The adventurous traveller was planning to carry out a wingwalk as part of her six-week stay in the UK, but was told she must get a doctor's certificate beforehand. For her 69th birthday, she base-jumped 192m off Auckland's Sky Tower.
She revealed she had only popped into Great Massingham post office and village stores on Friday, May 27, to claim her 10 pound winnings on a few scratch cards.
Ms De Gilio, who has also lived and worked in the UK for many years, said: "The lady cashier asked me if I wanted any more cards, and I saw this little wee sign on the wall, for EuroMillions.
"I bought five lucky dips, and it was the fifth line that won it. I did not listen to the draw the next day, but the following day we stopped at a supermarket - the Co-op in Bungay - after having dinner in Wymondham.
"It was the last one of my five tickets that made the machine produce two slips of paper. They just popped out.
"The lady on the counter turned to me and said it must be a big win and I needed to call Camelot.
"I called Camelot, but it was so windy, I could hardly hear. They said I had won 1 million pounds, and I replied 'What?".
Her plans for the money include a new house, health insurance and presents for her three daughters, seven grandchildren and seven great-grandchildren.
She added: "And I will spend it on travel. I've got friends in all corners of the globe and I can finally catch up with them. Top of my list will be Patagonia and Canada.
"But, as our father raised us to be independent, I won't go stupid with the money."
Her friend Mrs Marsden, from East Rudham, near Fakenham, said: "She's taking me with her to Bali and Lombok, which I'm really looking forward to.
"All I did was drive her to the shop to get the ticket.
"We met on a tour of China 12 years ago, and have been friends ever since.
"Life is one big adventure for Diana and I could not think of a nicer, more genuine person to win this life-changing prize.
"It's been so nice having her stay. I've had a millionaire mowing the lawns and cutting hedges all week."
nzh