This line is not from the book, but from the play in which Otto Frank returns to the annex in Amsterdam after the Russias arrived and liberated him and other Jews from Auschwitz. When he discovers Anne's diary, he peruses it, noticing her line, "In spite of everything, I still believe that people are really good at heart." Moved by her line of gratuitous charity toward mankind and the tragic end of a heart so generous in its love, Anne's father utters the final words of the play, "She puts me to shame."
After having been separated from her family and friends, Mrs. Frank lost her mind and fell ill in Auschwitz and died shortly thereafter in the infirmary barracks on January 6, 1945. Mr. Frank watched the others such as Mrs. Van Daan, with whom he had hidden from the Germans, taken off to the gas chambers. Then, having finally learned that Margot died and his favorite child Anne starved and finally died at the tender age of fifteen, Mr. Frank cannot feel this charitable about humanity.
The final words of Anne's diary underscore her words of hope:
...I twist my heart round again, so that the bad is on the outside and the good is on the inside and keep on trying to find a way of becoming what I would so like to be, and what I could be, if...there weren't any other people living in the world.