Her brother Youssouf Aitboulahcen said she had no interest in religion and only started covering her face with a veil a month ago.
In a statement, Mr Aitboulahcen said: “She spent her time criticising everything. She was living in her own world. She was not interested in studying her religion. I never saw her open the Koran. She was permanently on her phone, looking at Facebook or WhatsApp.
“I told her to stop all of this but she would not listen, she ignored my numerous attempts to give her advice.”
Three weeks ago, Aitboulahcen left her mother’s home to live with a female friend in Drancy, a suburb of northeast Paris. Then on Sunday – two days after the attacks – she rang him at 7pm
Mr Aitboulahcen said: “On Sunday at 7pm she called me because I had called her – and she sounded like she had given up on life.”