Borsellino was born in Palermo, Sicily, and worked there as a pharmacist. In July 1992 her brother, Judge Paolo Borsellino, was killed by the Mafia in a bomb explosion. She began to organise and participate in events such as public debates, rallies and protests against organised crime. These included events in France and Germany, such as an event in 1994 in Paris with the Argentinian organisation Mothers of the Plaza de Mayo.