I just finished a brief search about Ann Frank and have concluded that there is more then enough evidence that Ann Frank started her diary at age 13 and over the next few years she went back and edited her diary, condensing parts of it and rewriting other parts. There are three diaries, the last one unfinished.
Her father, the only survivor of the family edited her diaries with an eye to having them published.
Long story short: In 1959, Anne Frank’s manuscripts were studied by graphologists (handwriting experts) in Germany, as part of the preparations for a legal action that was brought by Otto Frank. In March 1960, the Hamburg graphologists came to the conclusion in their 131-page report that all the notations in the diaries and the loose sheets, and all the corrections and additions, were ‘identical’ with Anne’s handwriting. The report also concluded that the loose sheets were not written before the three diary books. Finally, the conclusion was made that ‘‘(...) the text published in German translation as Das Tagebuch der Anne Frank may be considered true to its sources in substance and ideas."
The most extensive investigation was carried out in the first half of the 1980’s by the Netherlands Forensic Institute at the request of the National Institute for War Documentation. The results of this research were presented in a report of over 250 pages. The main section of the report is taken up with the findings of a detailed handwriting comparison, but a forensic document analysis was also carried out....................
the report of the Netherlands Forensic Institute has convincingly demonstrated that both versions of the diary of Anne Frank were written by her in the years 1942 to 1944. The allegations that the diary was the work of someone else (...) are thus conclusively refuted."
The origin of the "ballpoint myth" is the four-page report that the Federal Criminal Police Office (the Bundeskriminalamt or BKA) in Wiesbaden, which was published in 1980. In this investigation into the types of paper and ink used in the diary of Anne Frank it is stated that "ballpoint corrections" had been made on some loose sheets. A Mr Ockelmann from Hamburg wrote that his mother had written the annotation sheets in question. Mrs Ockelmann was a member of the team that carried out the graphological investigation into the writings of Anne Frank around 1960.
http://www.annefrank.org/ImageVaultFiles/id_14671/cf_21/tenquestions_en.PDF
