"Very few people are blessed enough to call their father a legend, and an even smaller number are able to share that notion with the rest of the world," she wrote. "Today of all days I can genuinely say I am humbled by the outpour of love and support my family has received."
"Yesterday, I lost my best friend," she continued. "His kindness was infectious, and his grace, beyond compare.. And despite the worldly passing of an incredible man, I undoubtedly know heaven gained one stud of an angel."
Cassidy ended the tribute by citing a bible passage and referencing Frank's Hall of Fame career with the New York Giants, whom the sportscaster played for from 1952 through 1965.
Earlier Monday, Kathie Lee's Today co-host Hoda Kotb held back tears as she talked about her love for Frank. "He will be remembered with love," she said, adding that she was "grateful" to have known him.
Hoda shared that her co-host seemed remarkably strong as she coped with the death of her husband of 30 years, but that Kathie Lee was also "rejoicing in his life." "She said, 'Let me tell you what a tragedy is," Hoda said of her visit with Kathie Lee on Sunday. "'You know those little kids in the truly brave videos, some of the kids who didn't make it? That's a tragedy. Let me tell you about Frank Gifford.' She said Frank Gifford was a Hall of Famer, an incredible football broadcasting legend, and more than all that, he was a family man. He is a triumph. He got to live to almost 85-years-old."
The kind words didn't go unnoticed by Kathie Lee, who thanked Hoda and Jenna Bush Hager for the "beautiful tribute."
Thank you Hoda and Jenna for your love and beautiful tribute to Frank. I'm in tears.