[1] After coming up through Haukar junior teams, Sigrún played her first games in the top-tier Úrvalsdeild kvenna during the 2016–2017 season.
She helped Haukar to the national championship in 2018, scoring 11 points, including three 3-pointers, in the fifth and deciding game of the best-of-five finals series against Valur.
[3] On 1 March 2021, it was announced that Sigrún would return to the Úrvalsdeild and play for Fjölnir when her season with Chattanooga would end.
[7][8] Sigrún is the daughter of Gedur Gudjonsdottir and Ólafur Rafnsson, the former president of FIBA Europe.
[9] Her older sister, Auður Íris Ólafsdóttir, was a member of the Icelandic national team.