Koschischek made her international debut at the 2007 Military World Games in Hyderabad, India, where she earned a bronze medal in the 100 m freestyle by one tenth of a second (0.10) behind Romania's Camelia Potec, posting her time at 57.62 seconds. In 2008, Koschischek reached the semifinals of the freestyle and butterfly (both 100 m) at the European Championships in Eindhoven, Netherlands, with respective times of 56.15 and 59.61. Having cleared FINA B-cuts in both events, she guaranteed a spot on the Austrian swimming team for the Olympics.