"Of course my husband and family knew, but I only confided in one friend and one only, so it will be a surprise to a lot of people that know me. Even my parents didn't know."
She said she was "thrilled" to get her daughter Florence on the show as her model, adding that she had the "best day ever".
"That was more important for me than anything else," Caz said. "As a family, we don't generally use the word proud but I think on this occasion we will allow it."
The final show saw the remaining contestants - Caz, Orla and Yasmin - tasked with creating a bias cut slip dress, transforming sheer garments into a finale outfit, and producing a winning Trompe l'oeil outfit.
Young said she was "really pleased" for Caz and that she loved her final garment.
Grant added: "Caz pulled it out of the bag in spectacular fashion with so much courage, so much flair, so much beautiful technique. It was amazing."
Caz began sewing when she was 11 years old and made her own wedding dress 28 years ago but stopped for a period before her passion reignited during the Covid lockdown.
"I have gone and won something, I never win anything," she said. "I didn't think I would be able to do it. I remember after that very first catwalk, I rang my husband saying I am literally in awe of these people.
"When I was a child, I loved sewing and you have no fear as a child and you just sew anything. I think it's really important to get that fun back, that's why most of us sew, we sew for the sheer joy and the love of it, and I have got a lot of love for it."