Jonkers' began representing her state of Queensland at the age of twelve, and first represented Australia in 1999, winning a gold medal in that year's FESPIC Games. Her first Paralympics was the 2000 Sydney Games, where she placed fourth and sixth. At the 2002 IPC Swimming World Championships, she won two swimming silver medals. At the 2004 Athens Paralympics, Jonkers won two swimming bronze medals in the Women's 150 m Individual Medley SM4 and Women's 50 m Breaststroke SB3 events. She competed at the 2008 Beijing Paralympics, where she was one of Australia's oldest swimmers. She won a silver medal at the Games in the Women's 150 m Individual Medley SM4 event with a time of 3:28.88. In 2009, she set a world record in the 150 m individual medley at Australia's national short course championships held in Hobart. In 2010, she competed at the Queensland Swimming Age Multi Class Championships. She competed in the women's 100 m Breaststroke event, finishing third with a time of 02:50.59. In 2010, at the age of 30, she also competed at the 2010 Telstra Australian Championships the Over 12 years 150 m Medley event where she made the final finished with a time of 4:07.51. She also made the finals in the Over 12 years 50 m Breaststroke event. She was the Australian flag-bearer for the 2010 IPC Swimming World Championships in Eindhoven, the Netherlands, where she won a bronze medal in the 50 m breaststroke SB3 and was part of the 20-point 4×50 m relay team that broke an Oceania record.