Isn't this just glorious. One of those things a girl gets made to give to her beau. I have tried to find information online on dates this may have been in fashion, but I came up short. Speak to me of love, what a lovely sentiment to put on a photo of herself, Miss Ellen. Or maybe she was a Mrs.
I think it looks like the 1930's or 40's. Any earlier and I think her clothes would look a bit different, same if it were much later. I imagine it was given during a courtship or possibly an anniversary. If it were WWII, I think it would say something more along the lines of 'Don't forget me', or 'Stay safe', or 'Until we meet again'.
I like to imagine the story when I find things like this, the happily ever after if you will. This was placed in a book for safekeeping perhaps after they married and then children came and life got busy, as it does, and the photo was forgotten. I would love if anyone out in the universe saw this photo and could tell me who Ellen is/was and more about her life. But it's fun to see a stolen glimpse of her life in this photo.