Herlovsen began her career at Kolbotn IL. She made her debut with the club in 2004 and played for five seasons winning two league titles in 2005 and 2006 and winning the women's national cup in 2007. Following the UEFA Women's Euro 2005, Herlovsen drew interest from the women's section of English club Arsenal. The two sides met for negotiations, but were unable to reach an agreement. Later on, Herlovsen scored for her club Kolbotn in the 2007 edition of the women's Norwegian Cup. The players received their championship medals from the King of Norway.