at the newly inaugurated Great Ireland Run, but she struggled during the summer Grand Prix races. However, she appeared to be finding her form at the right time when she ran a season's best in the 3000 m in Zurich in a time of 8:37.55 on 15 August. At the World Championships in Paris later that month she was considered a possible medalist. She qualified very comfortably from her heat. However, in the final she finished last of the 15 starters. In December she finished an impressive fourth at the European Cross-Country Championships, and lead Ireland to silver in the team event. 2004 was to be an even more disappointing season for O'Sullivan. She struggled to find her best form throughout the year. At the Olympic Games in Athens, she qualified for the final of the 5000 m. However, in the final, O'Sullivan, who was suffering from an illness, finished last of the 14 finishers, well over a lap behind the winner Meseret Defar. She was given a hero's reception by the Crowd as she completed her last lap. It was one of the more poignant moments of the 2004 Games. In November, O'Sullivan finished an impressive 4th in the World Half-Marathon Championship in Delhi. In April 2005, O'Sullivan ran the London Marathon for the first time and finished 8th in a personal best time of 2:29:01. In June she won Dublin's Women's Mini Marathon for the second time. However an injury kept her out of the 2005 World Championships in Helsinki. In January 2006, O'Sullivan applied for dual citizenship, which would allow her to compete for both Ireland and Australia. This request was granted and she intended to represent Australia at the 2006 Commonwealth Games in Melbourne, but to represent Ireland in all other competitions. She was chosen for the Australian Commonwealth team for the 5000 m. However, she wasn't able to compete due to a hamstring injury. On 14 February 2007, O'Sullivan said she planned to retire after the Great Ireland Run on 15 April, having said the previous year that she planned to run competitively until the 2012 Olympics in London. She later confirmed that she would retire at the end of the 2007 season. In March 2008, O'Sullivan was appointed team manager of the Australian team for the 2008 IAAF World Cross Country Championships in Edinburgh, Scotland. In 2009, she ran the Cork City Marathon, 2010–present