LOADING RESULTS ... 
Did Anne Frank write her diary or was it written by her father Otto ?. This question gets asked over and over again.
Stuff like this appears all over the internet.
In 1980, because of a lawsuit in a German court, the German state forensic bureau, the Bundes Kriminal Amt [BKA], forensically examined the original "diary" manuscript. Their analysis determined that "significant" portions of the work were written with a ballpoint pen. Since ballpoint pens were not available before 1951, portions of the work were added well after the war (Anne Frank died in March 1945).
The BKA also determined that none of the "diary" handwriting matched known examples of Anne's handwriting. Earlier handwriting experts had determined that all of the writing in the "diary" was by the same hand. Therefore, the entire "diary" was a postwar fake.
The true author of the diary was Jewish novelist Meyer Levin, who demanded and was awarded $50,000 in payment for his work in a court action against Anne's father, Otto Frank.
and many articles and quotes like theses.
The diary has been praised for its literary merits. Commenting on Anne Frank's writing style, the dramatist Meyer Levin commended Frank for "sustaining the tension of a well-constructed novel".
"The Anne Frank Diary Fraud" by Brian Harring
"Is The Diary of Anne Frank genuine?" by Robert Faurisson
What the Anne Frank House say about it - http://www.annefrank.org/ImageVaultFiles/id_14671/cf_21/tenquestions_en.pdf
I guess we will never know the truth.