What did the narrator say about the origin of the story"The Frost King"?

Keller tells us that after her story was published, it was discovered to be very similar to another titles, The Frost Fairies. Helen decided that she must have been read this story as a small child, and she was deeply embarrassed that her own story was plagiarism.

Mr. Anagnos was delighted with "The Frost King," and published it in one of the Perkins Institution reports. This was the pinnacle of my happiness, from which I was in a little while dashed to earth. I had been in Boston only a short time when it was discovered that a story similar to "The Frost King," called "The Frost Fairies" by Miss Margaret T. Canby, had appeared before I was born in a book called "Birdie and His Friends." The two stories were so much alike in thought and language that it was evident Miss Canby's story had been read to me, and that mine was—a plagiarism. It was difficult to make me understand this; but when I did understand I was astonished and grieved. No child ever drank deeper of the cup of bitterness than I did. I had disgraced myself; I had brought suspicion upon those I loved best. And yet how could it possibly have happened? I racked my brain until I was weary to recall anything about the frost that I had read before I wrote "The Frost King"; but I could remember nothing, except the common reference to Jack Frost, and a poem for children, "The Freaks of the Frost," and I knew I had not used that in my composition.

Helen could not remember ever having heard the story, and she was questioned endlessly. In the end, she figured it all out.

Miss Sullivan had never heard of "The Frost Fairies" or of the book in which it was published. With the assistance of Dr. Alexander Graham Bell, she investigated the matter carefully, and at last it came out that Mrs. Sophia C. Hopkins had a copy of Miss Canby's "Birdie and His Friends" in 1888, the year that we spent the summer with her at Brewster. Mrs. Hopkins was unable to find her copy; but she has told me that at that time, while Miss Sullivan was away on a vacation, she tried to amuse me by reading from various books, and although she could not remember reading "The Frost Fairies" any more than I, yet she felt sure that "Birdie and His Friends" was one of them. She explained the disappearance of the book by the fact that she had a short time before sold her house and disposed of many juvenile books, such as old schoolbooks and fairy tales, and that "Birdie and His Friends" was probably among them.
The stories had little or no meaning for me then; but the mere spelling of the strange words was sufficient to amuse a little child who could do almost nothing to amuse herself; and although I do not recall a single circumstance connected with the reading of the stories, yet I cannot help thinking that I made a great effort to remember the words, with the intention of having my teacher explain them when she returned. One thing is certain, the language was ineffaceably stamped upon my brain, though for a long time no one knew it, least of all myself.
When Miss Sullivan came back, I did not speak to her about "The Frost Fairies," probably because she began at once to read "Little Lord Fauntleroy," which filled my mind to the exclusion of everything else. But the fact remains that Miss Canby's story was read to me once, and that long after I had forgotten it, it came back to me so naturally that I never suspected that it was the child of another mind.