According to the Chronicle of
Jan Długosz, Euphemia had a great and natural charm, and because of this she was also known as
Ofka. King Władysław II, Euphemia's uncle, wanted to make a close bond between
Kraków and
Upper Silesia, and for this reason he was probably instrumental in her marriage with
Bolesław I, Duke of
Cieszyn. Because Euphemia and Bolesław I were related in the third degree of consanguinity, a Papal dispensation was needed for the union, which was granted on 27 January 1412. The wedding took place ten months later, on 20 November, probably in the town of
Wiślica. In 1424, Euphemia and her husband took part in the coronation of King Władysław II's fourth and last wife,
Sophia of Halshany. After Bolesław I's death on 6 May 1431, Euphemia took the regency of the Duchy of Cieszyn on behalf of her minor sons, who inherited the lands as a co-rulers. She continued her husband's policies supporting the towns and in 1438 co-decided, with her son Wenceslaus I, to give
Cieszyn the right to mint coins. Despite her sons becoming legally able to rule by themselves, Euphemia continued to hold supreme authority over the Duchy. With her consent, her sons were allowed to sell the
Duchy of Siewierz to
Zbigniew Oleśnicki,
Bishop of Kraków, on 24 December 1443. On 29 November 1442 the co-Dukes of Cieszyn made a formal division of their domains; however, the unity of the Duchy was maintained during Euphemia's lifetime. She died before 17 September 1447 and was presumably buried alongside her husband in
Dominican church in
Cieszyn. ==Issue==