The proud mum went on to list the things she most admires about Kelsey Lee, who celebrated the occasion with a balloon in the shape of the number six, and a gift that she was clearly excited to open.
"I absolutely admire your tenacity when you want to achieve something, your strength when you may be sick & your love and the abundance of affection you have to offer," Kyly said.
"Watching you grow and develop into this stunning six-year-old who is full of life has made me the happiest Mumma bear. I love you Bella. Thank you for being you."
Kyly shares Kelsey Lee with her ex-husband Michael Clarke, who also took to Instagram to ring in his daughter's birthday.
Uploading a photo of himself smiling with Kelsey Lee, Michael wrote: "Happy birthday baby."
In the photo, the dad-and-daughter duo are grinning widely at the camera, as they stand in front of six cupcakes around a cake inspired by Tim Burton's The Nightmare Before Christmas.
While the birthday celebrations have only just begun, Kelsey Lee's parents will have to do something extra special this year to outdo her fifth birthday festivities.
Last year, Kyly spoiled her daughter with a lavish shopping trip, where she was able to fill her arms to the brim with all the toys she wanted.
"The deal was, as per what Kelsey Lee saw on YouTube, 'Mum, whatever I carry to the check out can I have, just for this birthday?'," Kyly explained at the time.