She was thrilled with Ernest Shepard's two-page reply but lost track of the letter as she grew up.
It was not until her mother, Marion Elphinstone, died recently that Karena, 37, found it among her belongings - and was told it could fetch up to £6,000 at auction.
Karena, from Eastbourne, received the letter when she was ill in bed,
She said: "I had flu and my mother suggested I draw a picture of my teddy bear, Emma, whom I was very fond of, and send it to Ernest Shepard because I loved Winnie the Pooh books.
"I asked him to improve my drawing and to my amazement he wrote a long letter back about a week later."
The late illustrator, who spent his last days in the West Sussex village of Lodsworth, after moving from Woodmancote, near Henfield, was 92 at the time.
As well as bringing Pooh to life, he also illustrated Kenneth Grahame's classic Wind in the Willows.
Drawing
Karena said: "It was a very nice letter about him and his family and where he'd had the inspiration for Pooh."
The letter revealed that Shepard's own bear, Growler, was the model for the honey-loving Pooh.
He also included a coloured drawing of Growler and told Karena about the bear's unfortunate fate.
The letter reads: "All my drawings for Pooh Bear are made from sketches I made of Growler.
"When the second war came, my son and his wife decided that she should go to Canada for safety.
"They went and took Growler with them. There, in Montreal, poor Growler was savaged by a dog and died.
"Please ask Emma to shed a tear for him."
Shepard also told the schoolgirl, now a mother herself, about friends he lost at the Battle of the Somme.
He wrote: "I was more fortunate and only suffered from gas."
Karena, a part-time cleaner, decided to auction the letter and drawing kept by her mother, fearing it might get damaged.
She said: "I was stunned when I was told how much they were worth."
The Sotheby's auction is taking place in May and Karena intends to be there.
AA Milne, author of the famous Pooh books, lived at Hartfield, near East Grinstead.
Now Karena reads Winnie the Pooh tales to her five-year-old daughter Marnie.
Karena said: "Marnie loves the books and she is a real Eeyore fan."
Emma bear is still also a member of the family, although, at almost 70 years old, she is no longer treated as a plaything.
Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.
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