Allen had an illustrious junior career, winning the 1989 and 1991 Pan American Junior Championships. She also achieved the rare feat of competing in three World Junior Championships. She never reached the final of the 400 metres, neither in 1986, 1988 or 1990. In the 4 × 400 metres relay she finished fourth in 1986 and 1988 and did not reach the final in 1990. Her six event participations at the World Junior Championships were unmatched for many years.