Kara (left) and Joan Kennedy
David Curran/Splash News Online
09/20/2011 AT 02:15 PM EDT
In the days following the sudden heart attack
that took the life of her daughter Kara Kennedy on Sept. 17, Joan Kennedy has taken comfort in remembering their recent time together at Joan's Hyannis Port, Mass., home.
"She had the most joyful good health this past summer," Kennedy, 75, tells PEOPLE about her daughter, 51. "That's why this is such a shock."
The summer had been an idyllic one, and the house was always full and included Kara's two children, Grace, 17, and Max, 15.
"She asked if she could have a dozen of her friends up, and it was so nice to have them sitting out overlooking Nantucket Sound," says Kennedy. "She was so happy to see her cousins and visit with friends. … I'm so grateful I have those memories."
Kennedy also spoke of the closeness Kara shared with her father (and Joan's ex-husband), Sen. Ted Kennedy, before his death
from brain cancer in 2009. (The Kennedys divorced in 1982 and had three children together: Kara, Ted, Jr. and Patrick Kennedy.)
"The last few years when he was sick, she'd sit with him the whole day and have her kids come by,” says Kennedy. "She was very calm and reassuring and loving to him."
Kara's funeral is being held Wednesday in Boston. Says her mother: "She will be buried at the Holyhood Cemetery in Brookline, where [her grandparents] Joe and Rose Kennedy are buried. If I'm feeling lonely I can talk to her at the gravesite. She was so loved by everyone who her knew her."