A teenage girl quickly became concerned for a classmate who was being held against her will in a Lavington park, a court has heard.
The 15-year-old was in a group of five girls targeting their classmate, who was robbed during the incident.
The girl slapped the victim at least once, Albury Children's Court was told on Tuesday.
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But defence lawyer Mark Cronin said his client then became very concerned and "did her best" in trying to protect the victim.
Mr Cronin said she conceded she did "a terrible thing" that she felt had "ruined her life".
"She told the group she wouldn't lie to police," he said.
Magistrate Rodney Brender heard how the girl stuck to her word and provided police with as much information as she could during an interview after her arrest.
Mr Cronin said the girl was "the least involved of the five in the offending" that took place at Black Range Park in Schaefer Street on December 17.
She also threatened to set the girl's hair on fire with a cigarette lighter and warned, after the girls' mobile phone and a bracelet were taken, that she would be "killed" if she reported them to police.
Mr Cronin's client was the first of the group to be sentenced.
She received a 25 per cent sentencing discount for her early guilty plea on the charge of take or detain person in company with intent to obtain an advantage.
The Director of Public Prosecutions granted her a further 25 per cent discount for assisting police with their inquiries.
On Tuesday she was placed on 12 months' probation, with a requirement that she not associate during that period with her four co-offenders.
Mr Brender told the girl, supported by her mother and stepfather, that without her early plea and assistance he would have doubled the probation period.
Mr Cronin said his client was now moving in the same circle as "good girls".
Also, the family was relocating to Queensland to escape bad influences on their daughter.