Bríet Sif came through the youth ranks of Keflavík[1] and played her first games with the senior team during the 2011-2012 season.
She started the following season well, scoring 10 points in Keflavík's 77-74 victory against Valur in the Icelandic Super Cup on 13 October 2013.
[4][5] Keflavík swept Haukar in the semi-finals in the playoffs and met defending champions Snæfell in the finals[6] where they lost 0-3.
She continued to improve during her second season with Stjarnan, upping her averaged to 13.0 and 3.9 rebounds while shooting 34.1% from the three point range.
For the season she averaged 13.4 points 4.3 rebounds per game and was named to the Úrvalsdeild Domestic All-First Team.