I did the same with The Red Pony! My art teacher, when I was 10, asked to borrow it and never returned it
I found a beautiful hardcover copy with a picture of a red foal on the front in a secondhand bookstore the other day.
Now, I read children's books. I reread them, and I read one's I've never picked up before. The simplicity is refreshing, the usually happy topics/endings make a nice change, I love to get caught up in fantasy worlds and if somebody bought me a copy of The Magic Faraway Tree, I would kiss them! There is quality writing in there.
Actually, my best friend got me The Roald Dahl Treasury as a birthday present two years ago, I thought it was fantastic. Maybe I'm an uneducated big kid? Your comment seems kind of snobby and frankly silly.
Did you ever consider she may have been reading it for work, class, or a myriad of other reasons? Not, that there is anything wrong with reading Harry Potter.
Kids books are fun! I will continue to read them, manga, and watch cartoons until the day I die.
LONG LIVE BIG KIDS!