Natalie Salmon was a student at a Venezuelan school where paedophile William Vahey was a teacher.
She told ITV News it is "really scary" that some of Vahey's victims may not know they had been assaulted, as they may have been drugged at the time.
She added she "can't believe" the teacher "got away" with his campaign of abuse for so long.
Vahey, who died in an apparent suicide, had been a teacher at several international schools across the world. The Southbank International School in London has confirmed that images of between 50 and 60 of its students were found on Vahey's computer.
Vahey was convicted over a child sex offence in California in 1969 but appears to have failed to sign the sexual offenders' register, which allowed him to slip through the net and go on to work in several schools.