Hi there! And thank you so much for sharing what you've found on her. It will reduce my researching up the wrong tree, as we also have a Katherine (Katie) Arn in our family and so far, I've found not a thing on her.
I have been rudely awakened by the number of different ARN branches there are in this country, after having lived most of my life believing our family of Arn's were the only ones. We're certainly not...my dad just moved way far away from the rest of them! Our ancestors appear to have clustered around Arnheim, Ohio and the Maysville, Ky areas. But I've just learned my grandfather, Dr. Fred Arn, took off for Illinois and lived there until he died in 1940.
Thanks again for your information on Katherine!