Terzić made her first impact in senior level athletics in the 2012 season. She won the silver medal at the 2012 World Junior Championships in Athletics with a Serbian national record time of 4:07.59 minutes for the 15000 m. A week later she took both the 1500 m and 3000 m titles at the Balkan Athletics Championships. She placed fourth in the 1500 at the Rieti Meeting and ran another national record in the non-standard 1000 m distance at the Athletics Bridge meet. In her final appearance in the junior category, she won the gold medal at the 2012 European Cross Country Championships. She celebrated the New Year by winning at the Silvesterlauf Peuerbach 5K road race, beating top marathon runner Irina Mikitenko.