Tang Hui was given 18 months of “re-education through labour” in the camp after she protested repeatedly outside government buildings that the men’s sentences were too low, the official Xinhua news agency said.
She had accused police in central Hunan province’s Yongzhou city of falsifying evidence to reduce the sentences of the seven men, who kidnapped and raped her 11-year-old daughter and forced her into prostitution.
Xinhua said she was released on Friday after her lawyer appealed the sentence. Authorities have agreed to investigate her claims that police falsified evidence, the report said.
The Hunan and Yongzhou governments could not immediately be reached for comment.
Tang’s case had caused public outrage, with many Chinese taking to the Internet to demand that the system of re-education through labour – often used to punish dissent – be scrapped.
“Please make abolishing the unconstitutional re-education through labour system the first step of political reform,” posted one on the popular Sina Weibo microblog.
“The resolution of this matter is so unfair. The state should protect citizens,” posted another.
Xinhua said Tang’s daughter was kidnapped in October 2006 and forced to perform over 100 sexual acts before she was rescued two months later.
Two of the accused were sentenced to death, four were given life sentences and one was jailed for 15 years.
The girl’s father, Zhang Hui, told Xinhua before the mother’s release that his daughter was still traumatised by the incident and would struggle to cope without her mother.
“Her mother is the closest person to her. I am afraid that she might break down or even try to kill herself if she realises her mother has been taken away to a labour camp because of her,” he said.