She said: "My mother was worried about losing her place at the golf club...my dad told me to grow up, even when I begged him to let me keep Nicola."
The detailed original post went viral and has now been shared by some 500,000 people, with thousands commenting on the geographical area that they've shared the post in and offering their support.
However, she told Holly Willoughby and Philip Schofield that she has also been subjected to abuse, and said she "will switch off Facebook" for a while.
One This Morning viewer tweeted about Fuller resorting to social media rather than an adoption agency: "Woman on This Morning says she can't afford adoption agency fees, yet lives a high life in France? Double standards."
Another viewer criticised the way that Fuller had approached trying to find her daughter. She wrote: "So selfish. There are proper channels for this, where everyone is protected. I feel for Nicola."
The heart-breaking letter posted on Saturday wrote of Fuller's anguish at giving up her daughter at such a young age.
She wrote: "I have lived 43 years with a tear in the cloth of my life, notwithstanding a wonderful daughter, a fine son and a whole possee of adopted/kids by marriage - but this pain will always linger with me."
She explains the circumstances of her daughter's birth: "You were born on 19th December, 1973 in Heath Hospital Cardiff. I named you Nicola.
"For 10 days, I learned how to bath you, keep you warm and cuddle you. You were with me for my 17th birthday on the 27th December that year."
And of the traumatic moment she had to let her daughter go, Fuller says: "On the morning of the 30th December it was snowing. I dressed you in your snow white layette, and took the lift down to the car park.
"A woman was waiting there and I couldn't let you go. There was an undignified struggle, and my mother wrestled you from my arms and handed you over.
"The woman turned and walked away, and I felt as if my heart had been ripped from my body. You were adopted through the Church of England Children's Society."
After saying she was shocked by the response her post had received, Fuller took to Facebook again to say she had no intention of "barging" into her daughter's life after she'd received some negative responses to the post.
She wrote: "I have no intention of barging into Nicola's life and threatening her equilibrium - all I want to do is open the door for her to walk through should she wish to."
She said she would "desist" in her quest to find Nicola if that's what her daughter wanted.