The girl, 12, was charged with assault with a weapon on Jan. 5 in Corner Brook. The girl pleaded guilty to the assault and was given probation for 12 months, and is now at home with her mother.
The mother is speaking out about what happened to her daughter while she was in custody.
The woman, who cannot be named because her daughter's identity is protected under the Youth Criminal Justice Act, said her child had self-inflicted cuts on her arm when she appeared in court.
"If the youngster was watched like they told me she was, why didn't they know anything about it?" the mother said.
"Why couldn't they tell me what happened or when it happened? Why wasn't my daughter brought to the hospital?"
Justice officials say a youth can be held in jail up to four days after their first court appearance, but must be kept separate from adult prisoners.
However, Carol Chafe, the province's youth advocate, said the experience can still be stressful for a young person.
"Sometimes when people are in lockups, they could be under the influence of alcohol," Chafe said. "They could be belligerent; that's not nice things for a young person to listen to."
The girl's mother said that holding a child in an adult prison is no way to help a child.
"Instead of giving the youngster the help she needs and getting her assessed, they throw her in an adult prison for two weeks," she said.
Justice officials will not comment on specific cases, but said that young offenders can sometimes spend up to four days in jail before being transferred to the youth centre in Whitbourne.
Chafe would not comment on whether her office will investigate the incident.
However, she said putting a minor in police cells for 11 days is excessive, by any standard.