Allen won the bronze medal at the 2002 ISSF World Shooting Championships in Finland. In 2005, she set a world record for shooting which stood for seven years. She also won the gold medal at the World Cup event in Belgrade, Serbia, and a silver medal at the European Shooting Championships. Allen shot for England at the 2006 Commonwealth Games, winning the bronze medal in the Women's skeet shooting competition. Competing for Great Britain at the 2008 Summer Olympics in Beijing, China, she placed in 14th position overall. She won two bronze medals at World Cup events in Dorset, England, and in Italy in 2010.