It was published in Speak of the Devil in 1967. I believe it might have been published in Seventeen magazine before that.
I first read this story probably when I was 40. It was in a paperback collection of deal with the devil stories.
It was so well written and with such a unique and creative plot. It is also just incredibly cute and sweet in a way.
I have probably read this short story at least 20 times. I have to stop myself from reading it too often or it might get ruined by being read too often.
I think it is one of the 3 best short stories I have ever read in my life.