Win McNamee/Getty Roberta McCain (left) and Cindy McCain in 2008
Hours after the death of her 108-year-old mother-in-law, Roberta McCain, Cindy McCain couldn't fully fathom that the family matriarch was gone.
"You're never ready for it," Cindy tells PEOPLE. "Never."
"She is going to be missed so much," says Cindy, 66. "She was a force of nature and someone I loved being around."
As Cindy prepared to fly east on Monday night to be with brother-in-law Joe McCain, who cared for Roberta for many years at her Washington, D.C., home before she died there Monday, Cindy shared that Roberta's health had diminished in recent months.
"She was failing," Cindy said Monday night. "[Joe] called me, maybe two months ago, and he said she's really starting to decline. And so she just peacefully went to sleep today, that's really what it was."
A cause of death has not been disclosed. But there had been other recent health struggles: Earlier this year, Roberta — an adventurous woman into her late 90s, who vigorously campaigned for son John McCain when the Arizona senator ran for president in 2008 — was hospitalized with pneumonia and was slowed by a mild stroke suffered about 10 years ago.
"She was not living her best life," Cindy says. "She hated the fact that she was unable to move around in the spirited way she was used to prior to getting sick."
At the end of Roberta's life "we never talked politics," Cindy says. "It was grandkids and all those kinds of things."
"Joe told her that [Meghan] had a little girl and I was going to send him a picture, I have it sitting on my kitchen counter and I was going to FedEx her the baby in a frame," says Cindy, who calls baby Liberty "adorable" and plans on meeting her this week. (Cindy says her trip after Roberta's death is her first since the novel coronavirus pandemic began.)
When Roberta and Cindy met some four decades ago, the elder McCain made an immediate impression, Cindy remembers.
"I was so astounded about how beautiful she was; when I met her, she was in her 70s — so poised and gracious and immaculately dressed," Cindy says. "She was something else, and she endeared herself to everybody."
Ida Mae Astute /Walt Disney Television via Getty From left: Roberta, Cindy and Sen. John McCain in 2008
As a mother-in-law, Cindy recalls a woman who "was always the kindest, nicest person to me."
"Throughout the 40 years I knew her, she never said an angry word to me, ever," says Cindy. "She always said words of encouragement. She always told me how nice I looked."
"She was a sweet, loving person, and she was grateful I was with John," Cindy continues. "I really hit the jackpot with her as a mother-in-law."
Roberta's close friend Greta Van Susteren told PEOPLE that "there wasn't a place in the world she hadn't been ... Every time I saw her she would say, 'Where are you going?' And when I told her and she'd say, 'Take me.' "
At John's 2018 funeral, after the longtime lawmaker died at 81 of brain cancer, Roberta — stoic in the front row — was photographed holding granddaughter Meghan's hand and "just couldn't believe John left before her," Cindy says now.
Cindy says that while details of Roberta's funeral are still being finalized, including if there will be Zoom for the many elderly friends of Roberta's who can't attend, she will be buried in Arlington National Cemetery with her husband, John S. McCain Jr., an admiral in the U.S. Navy and commander in chief of U.S. Naval forces in Europe who died in 1981.
As Cindy noted in a brief initial statement about Roberta's death, her mother-in-law is now reunited with her husband and two of her children.
"She was fun she was to be around — and how lively. She was like John, a force to be reckoned with. They were very similar in that respect," Cindy says. "A great deal of John's courage and honor and tenacity came from her. That is how she led her life and he, of course, was very much the epitome of her."
There was one question Roberta could never answer for Cindy: her secret to long life.
"I asked her 100 times and she couldn't tell me," Cindy recalls. "She said, 'Oh I just love living.' "