"To me, she is a real person," the author and advertising veteran told The Yorkshire Post.
It is this strong connection with the character that has led Mrs Walker to be creating her first film at the age of 58, based on the book - an idea first suggested by her father Peter Coldicott when she was a girl, and one which she again pledged to carry out during their final conversations on his death bed before he passed away last September.
Born in 1884, Jacob grew up in High Saint Agnesgate in Ripon and was a monocle-wearing entertainer who combined an acting career with writing 70 novels.
Compared by family to Halifax's Gentleman Jack inspiration Anne Lister, Jacob amused the troops in the Second World War with her humorous sketches, once refused an international award she was due to share with Adolf Hitler and went on to live in Sirmione, Italy, until her death in 1964.
Mrs Walker, who is married to BBC radio DJ Johnnie Walker, first found out about the novel when her parents packed her off to the Mediterranean country as a 16-year-old. Her father had previously found the book in a jumble sale.
"He said: 'Read this while you're out there. It's set in Italy, it's absolutely lovely. It would be a great film," she remembers.
It tells the story of a peasant, Antonia, a who has love affairs with two men from the English aristocracy after the First World War - one of which is rekindled years later through the power of her cookery.
Mrs Walker, who penned her own work about having cancer in Unplanned Journey, said of Antonia: "I just loved the book. I loved the character. She was a hard-working woman, she had an amazing talent for cooking. She also had this beautiful heart in her."
The novel was dedicated to a woman called Tina Ceci, who it is thought was herself an Italian peasant who married "above her rank", fueling suspicion among some that the work was indeed inspired by a real person.
"It's such a bizarre story to come up with, it feels like it has to be based on somebody," said Mrs Walker.
More than 40 years have gone by since Mrs Walker's father first said it could work as a film, and she has been planning it for a long time.
She said: "I've owned the film rights for something like 16 or 17 years.
"I've been having attempts at this, but unsuccessfully. I just don't think it was the right timing for it.
"My father gave this to me and I genuinely thought for a long time, this isn't going to happen until my father dies."
She continued: "The last conversation of his life was: 'Have you got any news on Antonia?'. He said: 'It was the one thing I wanted to know would happen before I died. I said: 'It will, keep the faith. I need you to work on this when you're upstairs'. After about three weeks, he did, and things started happening."
In a subsequent series of events Mrs Walker describes as "spooky", she kept meeting people who were able to "open doors" to finally start producing the film.
Renowned chef Angela Hartnett has come on board to create recipes and cook the food for the film - a fitting role for a figure whose own culinary ambitions were sparked by first her Italian grandmother and mother.
Director Justin Chadwick, whose credits include The Other Boleyn Girl, Mandela: Long Walk to Freedom and Bleak House, is also signed up.
Angus Thirlwell, the CEO of Hotel Chocolat, is joining Mrs Walker as a partner on the project.
Mrs Walker is raising funds for the film and getting a suitable cast in place for her script, and ideally wants to film in Lake Garda and at North Yorkshire locations such as Newby Hall, Scarborough and Helmsley next May and June, though no time frame is confirmed.
She originally planned to film the English scenes in the south-west - she splits her time between Shaftesbury, Dorset, and London - but a line producer who worked on the upcoming Downton Abbey film, which was shot at locations in Yorkshire such as Harewood House, recommended she bring the production to the region.
This also felt appropriate because of Jacob's origins.
She said: "I feel I'm being very true to her. I know that sounds sentimental, but why not?"
The project comes after 30 years of producing television commercials, a career she enjoyed but wanted to expand on.
Mrs Walker said: "I didn't want to die with my epitaph being: 'She sold a lot of cars and burgers'."
She added: "To be working on something that you really, really believe in, ultimately, is the greatest joy, but also the greatest pressure as well - it really matters to me that I pull this off, it really matters to me that it's a good film."
Who was Naomi Jacob?
Born in 1884, her parents ran the Ripon Choir School and her grandfather had been mayor of Ripon and the owner of the Unicorn Hotel.
Jacob trained as a teacher but quickly left education to become the secretary of a music hall star before becoming an actress in her own right.
Not long after starring opposite theatre veteran Sir Arthur John Gielgud in the West End, tuberculosis restricted her acting, so she took up writing.
Her first novel, Jacob Usher, was published in 1925, and some of her later books were set in the Ripon area.
In 1930 she moved to Italy for her health. For much of her life she had a house at Sirmione on Lake Garda, known as ‘Casa Mickie’ after the name by which her family and friends knew her. A plaque in her memory was put up in the town after her death in 1964.
During the Second World War, Jacob entertained troops as part of Entertainments National Service Association and was a regular broadcaster.
She was also politically active, first as a suffragette and then in Labour politics.
In her work she also spoke out strongly against anti-Semitism (her father’s family was Jewish), once publicly rejecting the Eichelberger International Humane Award jointly awarded to her and Adolf Hitler, according to Ripon Civic Society.
Jacob, who had relationships with women at a time when same-sex relations were much less open and who wore a monocle, suits and had cropped hair, had many celebrity, society and literary friends.
Among them was the novelist Radclyffe Hall, whom Jacob supported by appearing for in the defence during the 1928 trial for obscenity of her book The Well of Loneliness.
A plaque for Jacob was recently unveiled at her birth place in Ripon, and the ceremony was attended by Tiggy and Johnnie Walker.
After the unveiling Tony Atcheson, Jacob's great-nephew who lived with her and his mother in Italy as a young child, said: "Very much ahead of her time, she was a strong character who forged her own success with little support in an era when women were not afforded the same opportunities – much like another Yorkshire woman ‘Gentleman Jack’ had done some generations before."