Sofia Hjärne was a baroness. According to certain sources, she was instrumental in achieving the peaceful handover of the stronghold of Sveaborg near Helsinki to the Russians during the Finnish War in 1808-1809, thus averting a battle. She was the central figure of one of the earliest literary salons in Finland.
In 1831, she anonymously published Tawastehus Slott. En Romans fra Birger Jarls af Bjelbo tidehwarf (P), a romantic tale of Birger Jarl's sister's unhappy love for a Finnish chieftain, based on legend. Sofia Hjärne wrote anonymous poems for almanacs and newspapers and translated two plays.