[2] During her childhood, she was in regular contact with her Swiss relatives in Ticino and spent her summer holidays at her paternal family's house.
[2] Ersilia Fossati attended primary and secondary school at the Ghislanzoni Institute in Milan, in Italy run by the Ursulines of Saint Charles.
[4] In 1940, Fossati volunteered for the Frauenhilfsdienst (FHD), the Swiss Women's Army Auxiliary Service, in response to a national call from General Henri Guisan.
[3] Although Switzerland remained neutral throughout the Second World War, the country was prepared to defend itself from a potential Nazi invasion through National Redoubt plans.
The Frauenhilfsdienst was officially recognised in April 1940, and its female volunteers worked for the army in communications, logistics, and as medical orderlies.
Between 1942 and 1971, she worked on cataloguing dialect terms as part of the team run by Silvio Sganzini, a Swiss linguist, teacher and lexicographer, who was director of the Vocabolario dei dialetti della Svizzera italiana, an ongoing project recording and publishing the vocabulary of the dialects of Italian Switzerland.
[3][2] She is also a member of the foundation board of the Pro Senectute (de) section, which includes the canton of Ticino and the district of Moesa.
[7] Fossati served until 1983, and acted as a mentor to the next generation of Catholic women in Ticino politics, including Chiara Simoneschi-Cortesi.