“Everything was completely fine at the time but then in 2017, when the (Chinese government) policy on Xinjiang changed, she went missing and we later discovered she was in an internment camp for 10 months."
The Xinjiang region is home to more than eight million Uighurs. There are major human rights concerns surrounding China's detention of Uighurs.
Ms Yakufu was arrested in Xinjiang, in northwestern China, back in mid-2019. She had previously been released from an internment camp.
Ms Salay said she heard from her sister in December 2018, when she got a phone call out of the blue.
“She said everything was fine but she didn’t sound the same, she was reluctant to answer my questions and it felt like someone was monitoring the call."
Just four months later, she lost contact with her sister again.
Mrs Salay contacted Department of Foreign Affairs, who later informed her that Ms Yakufu had been arrested on charges related to financing terrorism.
“I'm really, really upset and angry because I know my sister is innocent, she is a good person helping my parents and we have the proof to show the money she sent was for the house.”
Ms Salay has provided SBS News bank transfer records and the contract of sale of the house her parents purchased in 2013.
The bank statements show a total of AU$135,000 was sent to Ms Salay's parents in Adelaide via three bank transfers in July 2013.
One transfer was made by Ms Yakufu and the other two by her aunt and uncle, who are also facing terrorism-related charges. Unlike Ms Yakufu, they have been granted bail.
SBS News has seen notices provided by the Kazakh Autonomous Prefecture for Ms Yakufu's aunt and uncle. It states: "The court has received the materials from Public Security Bureau... for prosecution against three people including Mayila Yakufu ... who are suspected of assisting with terrorist activities and unlawful possession of extremist articles."
Ms Salay said her sister has been on remand for 15 months and has had no access to lawyers or any family.
James Leibold, an expert in Chinese ethnic policy at La Trobe University, has reviewed the bank transfers and contract of sale documents provided by Ms Salay.
“The documentation on this is rock solid,” he said.
“What we see here is that she has got caught up in China's efforts to break the link between Uighurs back in Xinjiang and Uighurs overseas.
"They are trumped-up charges and unfortunately they have had and will continue to have a real human cost."
Mr Leibold said sentences related to terrorism offences vary widely, from a couple of months up to life imprisonment or even the death penalty.
Ms Salay acknowledges that there is little she can do but hopes speaking out may help her sister.
Rian Thum, a University of Nottingham historian who researches Islam in China, said an unprecedented crackdown started in 2017, throwing hundreds of thousands of Uighurs into prisons and camps for alleged “signs of religious extremism” such as travelling abroad, praying or using foreign social media.
The UN estimates at least one million people, mostly Muslim Uighurs, have been locked up in internment camps in Xinjiang. The Chinese government has repeatedly maintained these camps are "voluntary" camps and are used to counter extremism.
“At the time we started to see a massive number of people disappearing and later finding out people were in internment camps," Dr Thum said.
“It also became clear many of the people where being put in the camps for things they did quite a long time ago, for example listening to a sermon 7 years ago, anything the state could show possibly hinted to disloyalty."
He said charges like "facilitating terrorism" are commonly used as part of the crackdown.
“The definition of ‘terrorism’ is extremely broad and doesn't fit any global definition or scholarly deck definition for terrorism. Terrorism has just become a catchall for behaviour that makes the Chinese state nervous."
Ms Salay, who is 27 weeks pregnant with her second child, dreams of being able to see her sister again.
“I feel guilty sometimes we think we shouldn't let you send money to us, but it's not your fault. Not our fault. It's the Chinese government’s fault.
“I want the Chinese authorities to know what they are doing is wrong, they should release my sister as soon as possible, immediately and unconditionally because the evidence is we have evidence she's innocent and we have nothing to do with terrorism.”
The Chinese Embassy in Australia did not respond to a request for comment.
Correction: The amount transferred has been amended to AU$135,000. An earlier version of this story said it was AU$150,000.