In my opinion it would be better if you gave her the book yourself followed with a big hug and an ‘I Love You’!
My mother left a ‘birds & bees’ book for me in my room when I was a pre-teen. While the intention was indeed good it was a cold & distant approach. I did not feel like I was welcome to talk with her about it becuase she left no note or explanation. We never did talk about it & I always wished that she would have come to me instead of just leaving a book in my room.
Do what you think is best. Only my opinion.
God Bless,
Monica