Hello all! In 2011 during an interview to a Brazilian channel a journalist asked: “Queen Silvia, you have lived in Brazil from three to fourteen years old, so what space Brazil and the Portuguese language still occupy in your life today?” The queen then answered: “When my mother was alive we had a daily relationship [in Portuguese] as I used to call her frequently. With my siblings I naturally speak Portuguese too. Of course, nowadays it’s not every day anymore, but Brazil is in my heart and with the help of Child [the NGO she supports] I come to Brazil every year (…)”. In another interview to the written media she added: “I tend to speak Portuguese when I’m feeling happy!”
In fact, her first memories were in this language as she had relatives and friends while living in São Paulo (she arrived at three and went away as a grown teenager when her family moved back to Germany). So I assume that from 14 on she started using gradually more German. Undoubtedly she is gifted relating languages.
As a Brazilian native speaker myself I would say without any doubt that Portuguese must be her source/reference language, as she has practically no accent even after decades living abroad (she speaks Portuguese like any Br upper-class lady of her age). I still have to point out that she commits very minor grammar mistakes which are practically unnoticeable by most native speakers anyway. The only thing that gives away she’s not in daily contact with the language is when she switches a preposition for another in a saying, for instance, which is understandable given her distance to the daily practice.
So to sum it up, I’d would say she sounds completely native when she speaks Portuguese. Ah, and before I forget, a curious fact about her is that her mother (Alice Soares) had distant Amerindian roots, besides noble Portuguese.