After graduating with a masters in accounting from the University of NSW in 2019, Li Yuanjing went back to China to start her career at a top international firm in Beijing.
It didn't take long for Ms Li, who grew up in the nearby city of Tianjin, to make friends in the capital.
On her Chinese social media profile she used "tags" to describe herself as "a half-hearted stargazer", a wanderer and an extrovert who followed her intuition and feelings.
She posted about travelling across the world to capture a total solar eclipse, and shared star-watching tricks.
She met like-minded people online who soon became her social circle in real life.
Her friends say that on November 27 last year, Ms Li discussed in a Telegram messaging group attending a vigil for the families killed in an apartment-building fire in locked-down Urumqi days before.
She ended up going to the evening gathering which turned into a peaceful protest, with hundreds of participants chanting slogans against China's years-long zero-COVID policy.
The demonstration was one of a series in major cities including Shanghai, Nanjing, Guangzhou and Chengdu in late November that appear to have led to China dropping COVID restrictions.
Many demonstrators held up blank sheets of white paper, which became a symbol of their discontent.
While the police were there that evening in Beijing, they mostly refrained from intervening.
It wasn't until a few weeks later Ms Li and several of her friends were arrested. They haven't been heard from since.
'I'm very worried for her'
Steve, who asked to use a pseudonym because he feared retaliation from the Chinese government, went to high school with Ms Li and was in a stargazers group with her.
He said he was surprised when he found out she was one of the "A4 paper protesters".
He remembered her as a straightforward woman and even "a bit of a tech nerd" whose passion was "all about nature and science".
She had loved astronomy since she was a teenager and went out frequently to spot shooting stars, he said.
"I'm very worried for her," he said.
"Her WeChat account disappeared. When I read the news, I tried to check on her updates but it's like she has vanished."
'Picking quarrels and provoking trouble'
According to media reports confirmed by her friends, Ms Li was arrested on December 18 for "picking quarrels and provoking trouble".
Another three women — Li Siqi, a journalist, Zhai Dengrui, a teacher, and Cao Zhixin, a book editor — were also detained around mid-December and later charged, say their associates.
News about the protests has been censored in China.
According to foreign media reports and associates of the women, the police were investigating the motive of the protesters and whether there was "foreign power" behind them.
All four women were members of the Telegram group where they talked about the vigil.
After witnessing her friends being taken away by police again, Ms Cao recorded a video telling the public about what happened.
In the video, she said her friends and herself were all detained first on November 29 and let go after 24 hours.
She said they were told by the police at the time they were believed to be innocent.
The women hadn't expected to be arrested again, she said.
"When we thought it's all over … they quietly took a few of our friends away," Ms Cao says in the video.
"They were forced to sign blank arrest warrants. Police also declined to reveal the location, time and charge of their arrests.
"I have asked my friends to make this video public in case of my disappearance.
"So if you see this video clip, it means I have already been taken by the police."
The ABC has attempted to contact police in China.
Protesters and dissidents often face charges like "picking quarrels and provoking trouble" in China, with sentences of up to five years in jail.
The ABC was unable to verify the charges with local authorities or reasons for the women's arrests.
In China, the right to protest is enshrined in the constitution but in reality protests without government endorsement are seen as a threat to stability and considered illegal.
At least 10 other protesters have been detained across the country with some granted bail, while the status of others remains uncertain.
US-headquartered human rights advocacy NGO Human Rights Watch has called for all the protesters remaining in detention to be released.
A statement from the NGO said "a few" protesters were released on bail.
"More protesters are believed to have been detained or forcibly disappeared, though their cases are not publicly known, given the Chinese authorities' practice of threatening detainees' families to keep silent," it said.
Fears of speaking out
Tom, another friend of Ms Li who also asked to use a pseudonym, said her family did not want to talk to the media.
Even though he was not in China, he said he was concerned for his own safety speaking about Ms Li's situation because he had to go back to renew his student visa next year.
Tom said her friends were concerned and he had seen people discussing Ms Li's arrests in online chat groups.
"If I had been in China, I would have participated in the vigil in Shanghai too," he said.
UNSW said in an email to the ABC that the university was aware of news reports that Ms Li was detained in China following her participation in demonstrations against the government's zero-COVID policies.
The university said it hoped the matter would be resolved without delay and with due respect for legal principles and universal human rights.
A petition started by current students and alumni of UNSW calling for the authorities to free Ms Li has so far received more than 2,200 signatures.
The ABC has contacted the Chinese embassy in Australia but has not yet received a response.
