An unemployed woman with a low IQ, anger management problems and other psychiatric issues was placed on probation last November for threatening and assaulting a woman and her two young sons.
But just six months later, Elizerbeth Chua Hui Ping, 26, grabbed a 10-year-old girl by the throat at Boon Lay Interchange.
Two weeks after that offence, she choked a 14-year-old girl at the same interchange. Both victims were unharmed.
Chua was jailed for nine weeks and fined $600 on Monday. She had pleaded guilty to three charges: committing public nuisance, causing hurt and behaving in a threatening manner towards a person. Two other similar counts were taken into account during sentencing.
A community court heard that Chua regularly accompanied her father when he went to work as an SBS Transit bus driver.
On May 23, she scolded a woman who boarded her father's bus with a drink. The passenger then threw it away.
"However, (Chua) grew increasingly agitated and started shouting at commuters... and challenged them to fight her, causing annoyance to the commuters," said Assistant Public Prosecutor Dillon Kok.
The mother of the 10-year-old girl asked Chua to calm down but she became even more agitated and caught hold of the child and choked her.
Chua and the child's mother got into a scuffle and separated, and got into another scuffle even after the woman got off the bus.
Chua also chased the girl around the interchange but the child got away by hiding from her.
Chua was arrested and released on bail.
The following day, she grabbed a 14-year-old girl at the same interchange and choked her.
These incidents follow an earlier one in 2014 for which Chua was placed on 18 months' probation.
In that incident, she assaulted two brothers and their mother.