Bana Alabed said she had "no house" and had "almost died" following heavy shelling in the besieged eastern part of Aleppo where she lives.
Rowling, 51, sent an e-book to the seven-year-old after her mother messaged asking how her daughter could get hold of the Harry Potter novels.
Bana, whose account is managed by her mother, tweeted: "Tonight we have no house, it's bombed & I got in rubble. I saw deaths and I almost died."
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An earlier message posted on the account said: "Last message - under heavy bombardments now, can't be alive anymore. When we die, keep talking for 200,000 still inside. BYE."
Both messages were retweeted by Rowling.
An image of Bana holding a piece of card with the words "thank you my friend JK Rowling for the books" was posted on Twitter on Wednesday, after the writer's staff arranged for the gift to be sent.
She added in a tweet, "Love you from Aleppo - Bana", to which Rowling replied: "Love you too, Bana! Thinking of you, keep safe."
