Austria now plans to adopt tougher laws on sex crimes
The Austrian woman held captive by her father for 24 years was planning to move away from her parents' house shortly before she was locked up.
In letters written by Elisabeth Fritzl in 1984, and published on Thursday by the Oesterreich newspaper, she talks about her plans and hobbies.
Ms Fritzl, now 42, wrote the letters to a male friend just weeks before father Josef imprisoned her in his cellar.
Josef Fritzl has reportedly criticised coverage of his case as "one-sided".
He has, however, admitted holding Elisabeth captive and repeatedly raping her.
He fathered seven children with her - one of whom died when very young, three of whom were kept imprisoned in his cellar, and three others who went on to live with Mr Fritzl as his adopted or fostered children.
"After the exams... I'm moving in with my sister and her boyfriend," 18-year-old Elisabeth Fritzl wrote to her friend, named only as E, on 9 May, 1984.
In another letter dated 29 May, 1984, she writes about her hobbies - swimming, tennis and football - and how much she enjoyed going out with friends.
"I like to listen to music and day-dream. But if life is only made of dreams, well, I don't know," she wrote.
In a third and last letter from 3 August, 1984, just a few weeks before she vanished, she wrote: "Cross your fingers for me. When you get this letter, it will all be over. I'll give you my new address as soon as I've moved."
She includes a photo, on which she wrote: "Think of me! Sissy."
Earlier Oesterreich reported that Josef Fritzl had defended his actions, in comments relayed by his lawyer, Rudolf Mayer.
Mr Fritzl reportedly criticised media-coverage of his case as "totally one-sided", and added that he was "not a monster".
Mr Fritzl's alleged crimes came to light when Elisabeth's eldest daughter Kerstin, 19, became seriously ill.
She was allowed out of the cellar and admitted to hospital in Amstetten - where she remains in an artificial coma.
"Without me [she] would not be alive anymore... I was the one who made sure that she was taken to a hospital," Mr Fritzl said.
"I could have killed all of them - then nothing would have happened. No-one would have ever known about it," he added.
Elisabeth and five of her children are now in care with the Austrian authorities, who are protecting their privacy at a psychiatric clinic.