Gladys Wallace, 57, admitted that she was shocked the first time she saw her son — who was previously known as William — dressed as a woman.
But since then, the devoted mum insists they have become closer than ever — and enjoy girly shopping trips together.
Gladys, of Glasgow's east end, said: "I wouldn't say I was ashamed, but it was a bit of a shock to see your son standing there as a woman.
"It's like losing a son and gaining a daughter.
"We are closer now that she is Cassie than we ever were before. We go shopping together, we fight over shoes and she teaches me things about make-up.
"I can see the hormones taking effect now. She's becoming more and more feminine."
Gladys told how Cassie loved to play football and karate as a child — and gave no hint she was battling with her gender.
The proud mum said: "Never once did I dream of what was going on.
"I was completely surprised when I found out about Cassie.
"But as long as she is happy, it's her life and her choice."