The two women had created comedy magic in the legendary ’50s sitcom I Love Lucy — here, author Paige Peterson recalls their tight bond

On a summer day in August 1979, Lucille Ball came to Belvedere, California, to bid farewell to her friend and beloved costar Vivian Vance.

The two women had created comedy magic in the legendary ’50s sitcom I Love Lucy, with Ball as Lucy Ricardo and Vance playing her sidekick Ethel Mertz. But now, two decades later, Vance was dying of bone cancer, and Ball had come to say goodbye.

“You could hear them laughing, and towards the end there was a lot of sobbing,” says Paige Peterson, who’d grown close to Vance after the actress rented her mother’s home in Belvedere. “It was an amazing thing to witness. The love of these two women.”

Peterson shared the story of the stars’ final meeting with PEOPLE while discussing her new book, Growing Up Belvedere-Tiburon, which tells the history of the beautiful town located in Marin County, California.

On that day in 1979, Peterson remembers, “We had brought Viv down and she was lying on the couch in the living room. They ate lunch and they talked and talked. Viv knew she was dying.” (The breast cancer she had been diagnosed with in 1973 had metastasized into bone cancer.)

Peterson, who was in an adjacent room in case Vance needed her, remembers seeing Ball as she left. “The pain on her face shook me to my core. She was in tears. She couldn’t speak.”

“I think Viv gave up after that,” says Peterson.

Vance died a few days later, on Aug. 17, at 70 years old.

“She cried about losing Viv for months after that,” says Lucie Arnaz Luckinbill, the daughter of Lucille Ball and Desi Arnaz. “Viv was, in many ways, like a sister to my mother. She could talk to Mom like nobody else, and I don’t think my mother could confide in many people the way she would with Viv.”

According to Peterson, after Vance was first diagnosed with breast cancer and underwent a mastectomy and grueling chemotherapy, she moved to Belvedere from Salem, New York, “because she wanted a lifestyle change. The first house they [she and her fourth husband literary agent John Dodds] rented was my mother’s house.”

At the time, Peterson’s mother, an interior designer, told her daughter to bring some fabric swatches over to the new tenant (without telling her who she was). “I knocked and Ethel answers and I was stunned,” Peterson says with a laugh. “She said, ‘Come on in, honey,’ and I did. It was just one of those connections. We loved each other.”

Vance, who was about to go on the road for the touring show, The Marriage Go Round, invited Peterson, then working as a local actress, to audition. She got the part opposite Vance, and the two traveled all over the country and grew close. Afterward, Peterson would often help her out as a personal assistant. “She had become a mother to me and she loved ‘little Lucie’ [Lucie Luckinbill],” notes Peterson. “Lucie and I were the daughters she never had.”

While Ball and Vance had weathered a few ups and downs, the two shared a tight bond. As she watched them perform together, Peterson says, “Viv was so good at setting up the joke. She was so talented, and Lucy and Desi really loved her.”

Vance, originally from Kansas, was already a Broadway star when she was asked to play Ethel Mertz. Together, the show’s four stars — Ball, Arnaz (her real-life husband, who also played her husband Ricky Ricardo), Vance and William Frawley, who played Ethel’s cantankerous husband, Fred Mertz — created a hit.

After the show ended in 1958, Ball and Vance reunited on the sitcom The Lucy Show, from 1962 to 1968. This time, Vance’s character was named Vivian Bagley because as she once explained, “I was tired of people calling me Ethel.”

Peterson’s book, which contains many archival photos, is published by the Belvedere-Tiburon Landmark Society, where all proceeds will be donated.

“It’s a love letter to Belvedere,” says Peterson, who weaves her own story of growing up into the town’s history. “It was a railroad town, nothing glamorous about it. It was a sludgy place with barren hills and beautiful dairy farms.”

“We had enormous freedom,” she adds. “We’d make our peanut butter and jelly sandwich in the morning and put it in my bicycle basket, and we wouldn’t come home until the 4:30 whistle blew. There was nothing here, no houses.”

Fast forward six decades, and it’s now a posh commuter town with incomparable views of the San Francisco Bay.

Looking back, Peterson says, “Viv loved living in Belvedere. She moved to a home [the Farr Cottages] that was cantilevered over the bay and would sit and read for hours on the deck, where she could look at the most beautiful view in the world. She loved the simplicity and the quiet of living here.”

In her final days, she says, “Viv was in the place she loved most. And that’s how she left the world.”