Here are two books from the past, recently updated. I haven’t read them, but they seem to be popular in Christian circles today.
The first is Beautiful Girlhood (1922), by Mabel Hale. It is available in Kindle edition for $0.99 here.
It was updated by Karen Andreola, available here.
The second is Winsome Womanhood (1900), by Margaret Sangster (not Margaret Sanger). You can read it in free .pdf here.
It was lightly revised by Shelley Noonan and released as Beyond Beautiful Girlhood, the “next step in the Beautiful Girlhood series.”
I generally prefer original to updated versions. But, if you want a 14yo girl to read it, it can help to have a more contemporary tone.