Reilly, born in Geraldton, Western Australia, and growing up in Perth, Western Australia, was a strong junior swimmer winning four gold and two silver medals at the 1998 Australian Age Championships and later that year at the 1998 Commonwealth Games in Kuala Lumpur, at the age of 15, won her first international medal with third in the 400-metre individual medley.

In 2000, after now competing in three international meets, she continued her great form at Australian Age Championships picking up three gold and two silver medals.

In July, at the 2002 Commonwealth Games in Manchester, England, she won first gold medal in an international meet taking out the 400 metre individual medley in a time of 4 mins 43.59 sec.

She backed this up in August, at the 2002 Pan Pacific Swimming Championships in Yokohama, Japan, winning gold in the 400-metre individual medley in a time of 4 min 40.84 sec.

In April 2003 at the inaugural Mutual of Omaha Duel in the Pool in Indianapolis, Indiana, she won silver the 400-metre individual medley.

In August at the 2006 Pan Pacific Swimming Championships in Victoria, British Columbia, Canada, she failed to the make the final of the 400-metre individual medley finishing 12th overall.