Carole, 55, broke her silence on Instagram Sunday February 17, two days after the 85-year-old passed away.
"She was loved. ❤️ Rest in Peace, Lee," the author wrote along an old picture of Jackie Kennedy's sister.
The journalist also had a message for her followers.
"Thank you for the kind words & comments. ?," she ended the post.
Carole, who was married to Lee's son Anthony Radziwill, remained close with her mother-in-law even after her husband lost his battle with cancer in 1999.
During an interview with OKmagazine.com in 2015, she revealed they had a "beautiful relationship," and discussed their special bond. "I really enjoy seeing her, spending some time in New York, some time in Paris. I adore her," she added. 'She’s still as gorgeous as ever."