Complex sentence: Anna Ulrica Arfvidsson (1734--1801), was a Swedish fortune-teller during the reign of Gustav III of Sweden and commonly known as "Mamsell Arfvidsson" (Mademoiselle Arfvidsson).
Split into simpler sentences: Anna Ulrica Arfvidsson (1734--1801), was a Swedish fortune-teller during the reign of Gustav III of Sweden. She was commonly known as "Mamsell Arfvidsson" (Mademoiselle Arfvidsson).