She is a teacher and co-founder of the Meeting per l’amicizia fra i popoli. She taught Italian and Latin in high schools and co-founded educational and cultural works. From 1971 to 2014, she taught in state high schools and then in the private high schools of the Karis Foundation in Rimini, with which she had collaborated since its inception. 

 Since 1980, she has shared responsibility for the Meeting for Friendship Among Peoples Foundation, of which she was President from 1993 to 2020. The history and development of the Meeting have led her to have significant encounters in many parts of the world. The Italian Embassy in Moscow, the UNESCO headquarters in Paris, the Library of Alexandria in Egypt, the Palace of Doctors in the Temple of Mount Koya in Japan, and the United Nations headquarters in New York are some of the places where Guarnieri has spoken as a speaker in public meetings. She has encountered many personalities, including Pope John Paul II, the Dalai Lama, Rabbi David Rosen, Cardinal Ratzinger, Secretary-General of the Muslim World League Abdul Karim al-Issa, the Grand Imam of Al-Azhar Ahmed A-Tayeb, Carlo Rubbia, Sergio Marchionne, Francois Michelin, and Riccardo Muti. 

 She has participated in cultural and editorial initiatives. In 2001, she collaborated on the editing of a commented edition of the Divine Comedy published by Bur Rizzoli. She is currently a member of the Scientific Committee of the Unicampus San Pellegrino Foundation. 

 In 2004, she received the Sigismondo d’Oro award, conferred by the Municipality of Rimini to citizens who have honored the city with their activities. In 2020, she was awarded the honorary title of Grand Officer of the Order of Merit of the Italian Republic by the President of the Italian Republic, Sergio Mattarella.