The funeral was held in her hometown of Sulmona, in the central Abruzzo region, on Monday.
Di Lorenzo, who had been living in Berlin for several years and worked for a German transport company, was among the 12 people killed after a truck ploughed into the busy market on December 19th.
Her mobile phone was found at the scene and death confirmed after DNA tests.
"The pain at her death is great," Mattarella said.
"Once again, one of our young compatriots has been the victim of the senseless, execrable violence of terrorism. I express the solidarity and closeness of the whole country to Fabrizia's parents and brother."
The terrorist attacks in Paris in November last year also claimed the life of Valeria Solesin, a 28-year-old from Venice.
Anis Amri, the suspected Berlin truck attacker, was gunned down by an Italian police officer in Milan on Friday. He is suspected to have transited through the French city of Lyon by train.