George died in 1471; Joanna wanted to fulfill his political testament and helped to enforce acceptance of Polish prince Vladislaus Jagiellon on the Bohemian throne.

In 1473 queen dowager and new king Vladislaus launched a provincial diet in Benešov, where they sought to remind to gathered Estates the political legacy of Joanna's husband and his constant effort to achieve religious tolerance and lasting truce between Catholicism and Utraquism in country.

After 1473 Joanna withdrew from political life and moved to the traditional place of Bohemian widowed queens, one of her so-called dowry towns, Mělník.

She bequeathed six thousand threescores of Prague groschen for renewal of local royal collegiate chapter of St. Peter and Paul, defunct at the beginning of the Hussite Revolution.

According to her last will she wished to rest in local Church of St. Peter and Paul but other sources indicate that she was finally buried in royal burial vault beneath the St. Vitus Cathedral in Prague, alongside her husband George.