The proof is in the front of the book, The Lion, the Witch and the Wardrobe, in the letter to Lucy.
Owen Barfield, a close friend of Lewis since 1919, married musician and choreographer Maud Douie (1888–1980) in 1923. They had two children: Alexander, born in 1928, his younger sister Lucy, born in 1935. Geoffrey, born in 1940, was a foster child. In May 1949, Lewis sent Lucy the completed manuscript of The Lion, the Witch and the Wardrobe with a letter in which he said: "I wrote this story for you." In October 1950, when the book was published, this letter became its dedication (in September 1952, Lewis dedicated his "The Voyage of the Dawn Treader book" to Geoffrey): -
Lucy was born in Carlisle, Cumbria, on 2 November 1935. She was a very lively, friendly and happy child. From an early age she trained hard to be a ballet dancer. She also showed marked musical taste and ability as well, and later taught dance and music at a Kentish school for girls.
She was also interested in her father's work and accompanied him in 1965–66 during his second visiting professorship in America at Brandeis University. Lucy Barfield, then 30 years old, was a piano teacher at the local music school in Cambridge, Massachusetts. At the end of the school year Lucy's mother Maud joined them and, as part of their holiday, the three went together to visit Owen Barfield's friend Professor Craig Miller in Vancouver. Upon their return to England, Lucy was diagnosed with multiple sclerosis.
Soon she began her slow, remorseless decline towards helplessness, alternating with occasional heart-rending periods of remission. Lucy bravely fought her disease, even trying to continue dancing and teaching. But after a while she could not leave her home and finally even her bed. In 1968 she had to be hospitalized.
In 1977 Lucy had to be hospitalized for the second time. Then, in June 1978, she married her friend Bevan Rake (1921–1990). But in 1990, after Bevan died of a heart attack, Lucy had to return to the hospital. She was never to leave it again.
Her body continued to decline. For the last five years of her life she was unable to move, speak or feed herself. However she continued to fight her disease becoming an inspiration to everyone who knew her. Walter Hooper writes in his obituary and also Paul Ford notes it in his Companion to Narnia: "As every creature comfort was taken from her, Lucy's faith in God grew and blessed not only her, but also those who knew her. Owen Barfield, touched by her humility, said many times, "I could go down on my knees before my daughter."
Her mother died in 1980, her father in 1997. Her brother Alexander visited her often. She liked to listen to Geoffrey reading her the Chronicles of Narnia over and over again. Lucy Barfield died at the Royal Hospital for Neuro-disability in west London on 3 May 2003, having battled multiple sclerosis for nearly 40 years.