A little girl's gift

I read this book over 40 years ago as a adolescent but I still remember how it touched me. It was about a little girl who became ill on the way home from school one day, and through tests they found that she had Leukemia. It tells the story right up to her death and her wish to donate her organs..thus the title "A Little Girl's Gift". I remember pleading with my mother to tell me how to get an organ donation card, which she did. Few books in my life have stayed with me, as this one did.