Lawyers for the woman in the US say a "cease-and-desist" letter was sent by a US law firm in December, on behalf of Andrew Tate and his brother Tristan.

The letter threatened to sue the woman and her parents for $300m (£249m) if she did not retract her statements.

A lawyer for the Tates said they were pursuing valid claims for defamation.

The BBC has seen a redacted copy of the letter, apparently sent on behalf of the brothers.

"In April 2022," it reads, "you falsely stated to a third party that our Client human trafficked you, abused you and held you against your will […] You have repeated false and defamatory statements to the police, the media, and another United States citizen about the Tate brothers."

Andrew and Tristan Tate are currently being held in preventative custody in Romania, while police investigate allegations of trafficking and rape, which both men deny.

Benjamin Bull - who works for the National Centre on Sexual Exploitation - says his client is a key witness in the Romanian investigation, and that the letter was designed to do "one thing and one thing only":

"[It] was intended to shut down the witness; stop the witness from bringing testimony forward in any proceedings," he said.

"They want these young ladies to climb into a hole and hide, never come forward [or] describe what they saw and what happened to them. It's clearly an effort to intimidate."

Lawyers for the Tates have confirmed to the BBC that the cease-and-desist letter was sent in December, as a civil matter for defamation and slander in the US, but deny any intimidation.

Tina Glandian, one of their legal advisors, said there was nothing abnormal in them pursuing valid legal claims for defamation. "The fact that [the Tates] are incarcerated right now is not a basis for them not to pursue their legal rights," she said.

The investigation into rape and trafficking allegations is believed to rest, at least partly, on the testimony of six women. No charges have yet been brought.

The Tates' legal team have also revealed that the brothers filed criminal complaints in Romania last April against two women, including the witness who received the cease-and-desist letter in December.

Ms Glandian said the criminal complaints in April were filed in response to allegations that two women were being held against their will by the Tate brothers.

"There was no evidence whatsoever of that," she said, "which is why [the Tates] were not arrested in April. [At that time], they were nothing but victims of false allegations, and they had every right to file criminal complaints for having their homes raided [and] property seized."

The results of those criminal complaints are still pending, she says.

Benjamin Bull, who represents some of the witnesses in the current Tate investigation, says the impact of legal action on his clients has been upsetting and intimidating.

But Dani Pinter, part of the same legal team, says it is not just the threat of legal action that is intimidating, but the online harassment many of her clients receive for speaking out.

"Regular, high production value videos, meant to embarrass and harass them, are shared among Tate's followers," she told me.

"Making really salacious claims, attempting to slut shame them, saying they're liars. But included in that is their private information - where they work, who their family members are - with the clear intention to incite harassment. And it's working."

The two alleged victims she represents have been getting death threats, she says.

"They're scared to death. They're both in hiding. They feel they can't settle anywhere, because people are trying to find them."

Prosecutors have been careful to keep the names of the six women in their case strictly confidential. But some have had their full names published on social media.

And the names of two witnesses even appeared in a statement to the BBC from the Tates' US communications team. The BBC is not naming them publicly.

Andrew Tate and his brother have no access to their social media while in custody, but they've built a vast and loyal network of fans and supporters who are very active online.

Some accounts appear to be fully-staffed operations, regularly releasing videos and documents designed to undermine the testimony of witnesses and other women making allegations against the Tates.

Earlier this week, one of the most active accounts published the full name, social media handles and WhatsApp messages of one of the alleged victims in the investigation.

The BBC has approached the account for comment, but has not yet received a response.

Even those who barely break the surface of this story can find themselves a target.

Daria Gusa spoke to the BBC and others about receiving a private message from Andrew Tate's Instagram account when she was 16 years old. It followed the same pattern laid out by him in online speeches about how to win a woman's attention and gain influence over her.

She did not allege that he had committed any crime.

"I got a bunch of messages," she told me. "Most were from people saying I was lying or calling me a slut."

But she also received "10 to 15 threats" online.

"I had a guy texting me, telling me 'I know you're studying at this university, the schedule is published online, I know where you are'" Daria said.

Several of her friends, who also appear to have had contact with him, have refused to speak out about their experiences, she says.

"It's not just the people who work for him," she explained. "It's that there are basically millions of men out there who really idolise these people, and would do anything to protect them and their image, so I think it's completely justifiable that so many girls don't want to speak out."

It is not clear exactly who runs some of the most active accounts defending the Tates, or how much cooperation exists between them.

But the risks for women making public allegations against Andrew Tate can be high, and they can come from many directions.