At the 2013 World Championships in Athletics, which was held in Moscow, Viljoen took only the 6th place with a mark of 63.58 meters. In 2014, she placed second at the Commonwealth Games. Later that year she won the African Championships with a result of 65.32m. Viljoen won a silver medal, coming in second to Israel's Marharyta Dorozhon, at the IAAF Diamond League Bislett Games in Oslo, Norway, on 11 June 2015.