Halko started out in parasports at the age of seven after being approached at a farmer's market by a member of the Greater Oklahoma Disabled Sports Association. She had never used a wheelchair prior, but uses one to race. Classified as a T34 athlete, she entered her first senior competition in 2015, competing at a Grand Prix in Mesa, Arizona. That same year Halko was chosen to represent the United States at the 2015 IPC Athletics World Championships in Doha. She entered three events and won silver medals in two, the 100 metres and the 400 metres. In both she was beaten by Great Britain's Hannah Cockroft, the long-time dominant competitor in the women's T34 sprint events, but with a time of 18.55 seconds in the 100 metres, Halko set a new North America record.