Guðný made her senior international debut for Iceland in a 3–0 win over Portugal at the Laugardalsvöllur Arena in June 2006.

At UEFA Women's Euro 2009, Guðný was included in the squad but did not play in any of the matches as Iceland were eliminated in the first round.

[1] At the 2013 European Championships in Sweden, Guðný suffered the fourth anterior cruciate ligament injury of her career at the age of 24.

[2] Guðný made another comeback, but injuries eventually forced her into retirement at the age of 26 in May 2015.

This biographical article related to women's association football in Iceland is a stub.