A friend of the woman who complained about the behaviour of Red Bull F1 team principal Christian Horner says she has been left “very upset, scared and lonely”.

In fresh claims made by a family friend, Horner’s accuser has been silenced after signing a Non-Disclosure Agreement which prevents her from discussing the matter with anyone other than her father and brother.

“It’s impossible for people to understand what it’s like for her,” the friend told BBC Sport. ”She can’t talk and she won’t talk.

“But I can tell you what it is doing to her. Every time I have asked her something, she breaks down in tears and says she’s got no-one to talk to because she’s not allowed to talk.

“She is very upset, very angry, very scared, very intimidated, very lonely. And I think it’s impossible for people to understand without being in her shoes what it’s like for her.”

A spokesman for Red Bull said: “Both parties signed a confidentiality agreement on it so they both can’t discuss it.”

Horner was cleared of misconduct following an investigation by Red Bull’s parent company and has always denied the claims.

But when a cache of messages purporting to involve Horner was leaked to senior F1 personnel and media on the eve of the season-opening Bahrain Grand Prix, the controversy immediately returned to the spotlight.

Horner refused to comment on what he described as being “anonymous, speculative messages from an unknown source”, but the friend claims the apparent exchange was genuine.

“We can all read the WhatsApps and anybody can come to their own conclusion whether that was an appropriate relationship between a CEO and a PA,” the friend said.

“As Christian has said, he wants to draw a line under this. Well, if this has been a fair and independent process and there has been no wrongdoing found, then why isn’t that being brought forward in a transparent way and why isn’t Christian denying that those WhatsApps are real?

“I do feel like you had some people who feel it takes two to tango, but that’s unfair. That is trying to divert. The issue here is, should Christian have done what he did as a CEO?”

The complainant, who has been suspended on full pay, is believed to be appealing against the inquiry verdict.

According to her friend, she “struggles to understand” how Red Bull dismissed the allegation.

“She is determined for the truth to come out,” the friend continued. “She just wants to work in the sport and is very concerned about her reputation and ability to get hired by anyone.

“She has been in motorsport her entire life, so on one hand she is very concerned and scared for her future, on the other hand very determined for the truth to come out.

“Because she can’t talk to her friends openly, I think she has all this bottled-up fear and concern that she is not able to openly communicate with her friends and family to support her and give her advice, because she is being respectful of the terms and conditions that have been placed upon her.

“It’s pretty clear she has not been able to say a word or even identify herself and yet Christian is able to give enough commentary because he has got a position of power and influence to effectively give his side of the story and she has been completely muted.”