Bosnyák was the daughter of Baron Tamás Bosnyák and Mária Kenderes. At the age of seventeen, she married Mihály Serényi, captain of Fülek (Filakovo) and Szendrő Castles, but the marriage lasted only for a few months (until Serényi's death in March 1626). After the death of her first husband, she returned to Nagysurány to her parents. Later that year, her mother died, and in the following year, she lost her 22-year-old brother. Her father was serving in Fülek Castle at that time, so it was she who dealt with the management of their estate. Soon, she became known by the neighborhood as a generous supporter of the poor and the sick. At the age of 21, as a result of the mediation of cardinal Péter Pázmány, she married Ferenc Wesselényi. They lived in the Sztrecsnó (Strečno) Castle and had two boys, Ádám (1630) and László (1633).
After Bosnyák's father died of cholera in 1634, her husband Ferenc Wesselényi took over the duty of the captain at the Fülek Castle. Wesselényi rarely came home to his family which, in the meantime, moved to Vágtapolca (Teplička nad Váhom) on account of many attacks against Fülek by Turkish soldiers. The management of their estate and the care of the children remained the duty of Bosnyák. In Vágtapolca, she took care of the poor, and with her husband, she founded an almshouse in the village which also served as a hospital. People of the neighborhood thought of her as a living saint.
Later Wesselényi had an affair with Mária Széchy, known as the Venus of Murány.
After her second husband's affair, Bosnyák donated even more than before to the poor and at nights, she went to pray in the chapel. According to a legend, she had a vision in which the Virgin Mary appeared and warned her to pray.
Bosnyák died at the age of 35 and was buried in the castle chapel.
In 1689, the castle changed hands, and the new owner decided to transfer the remains of the Wesselényi family members who were buried in the castle. During the transfer, the mummified body of Bosnyák was found which was later transferred to the church of Vágtapolca.
On April 1, 2009, a 31-year-old mentaly disturbed man from nearby town of Žilina broke the glass cover of the coffin and lit the mummy on fire after entering the church with a key obtained from a nearby confectioner shop. The mummy has burned to cinder within minutes. The man, who was thought to be suffering from schizophrenia, was sent to a psychiatric clinic. He claimed that Bosnyák was a vampire, and came to haunt him at night.
- "Podpaľač ostatkov Žofie Bosniakovej sa lieči na psychiatrii". 2 April 2009. Retrieved 23 May 2011.