JC and Sofia did a State Visit in 2008, no tiaras at the gala dinner either
Casa de Su Majestad el Rey de España - Actividades y Agenda - Viaje de Estado a la República de Perú
Sofia just wore Tiaras for state visits abroad in the 70s, as princess and later in the first years of JC reign, she also wore a Tiara for state visit to Austria 1995. I think she always was "mixed up" wearing a Tiara or not , i remember the berleburg wedding she wore no tiara, while other royals wore a tiara the same with state visits, while other Royals "mostly" wore a tiara also for black tie she usually waived. So far leti had just one state visit a tiara was appropriate but she wore no tiara ( Portugal) i hope this will chance for upcoming state visits of course not likely she will change)