"TikTok was her world. And YouTube. That's how she spent her time," the girl's father Angelo Sicomero was quoted as saying in Saturday's Corriere della Sera newspaper.
Prosecutors in Palermo are investigating that case, which has led to increased scrutiny of children's use of social media platforms.
TikTok, owned by the Chinese company ByteDance, first gained popularity in Asia and now also has a big following in the West. It has become hugely popular among teenagers in Italy during the COVID-19 pandemic.
The Italian regulator said TikTok had agreed to block all accounts in Italy from Feb. 9, and to readmit only users who provided a date of birth showing they were at least 13 years old.
The regulator said TikTok had also agreed to evaluate using artificial intelligence to detect under-age accounts.
It will, however, have to discuss the proposal with the Irish privacy authority, which is the European Union's lead data protection authority for Tik Tok because the firm has its European head office in Ireland.