Jiang Rong, her husband Pastor Wang Yi and members of the Early Rain Covenant Church in Sichuan were arrested on 9th December 2018 after being accused of inciting subversion.
Rong spent six months in prison before being reunited with her son.
Christian Solidarity Worldwide's (CSW) China researcher told Premier it couldn't guarantee Rong wasn't mistreated in prison.
"Because of the nature of the kind of detention she was placed in, we don't know a lot about what condition she was in, about whether she was mistreated - although mistreatment is quite common in the type of detention she was placed in," she explained.
According to a Facebook page 'Pray for Early Rain Covenant Church', there are five members of the church - including the pastor - still in detention.
Between 20th and 31st December, authorities closed churches and confiscated materials from unregistered church groups in Anhui, Inner Mongolia and elsewhere in Sichuan, and prevented or interrupted Christmas celebrations in many places across the country.
CSW's Chief Executive Mervyn Thomas said: "While we welcome the news that Jiang Rong has been released on bail and reunited with her son, we strongly condemn her six month long detention and the charges against her, which are completely unfounded.
"For half a year, Jiang has been arbitrarily deprived of her liberty and kept apart from her son.
"We call on the Chinese authorities to drop all charges against Jiang, to release immediately and without condition all Early Rain Church members still in detention, and to cease all forms of harassment against the church."
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