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.”
Roberta did not get to meet her newest great-grandchild, Meghan McCain’s daughter, Liberty Sage, who was born on Sept. 28. But she lived long enough to learn about the happy news.
“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.
When Roberta and Cindy met some four decades ago, the elder McCain made an immediate impression.
“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