Harnasko has won numerous medals in the Junior World Cup and Junior Grand Prix series. She briefly competed as a member of the Belarusian Group that competed at the 2015 European Junior Championships where Belarus won Group silver in the All-around and gold in 5 Balls. Right after, she started competing as individual again. On October 16-18 she competed at International Tournament Tart Cup, where she took bronze medal in Junior All-around (59.500), behind Anna Sokolova and Maria Sergeeva. This was her first individual competition that year.