The "betrayed" ex-lover of a married Perth businessman has avoided being sent to jail for threatening to expose their affair if he did not pay her at least $150,000.

Rachel Roche, 40, met the man, whose identity is suppressed, in 2019 on the dating website seekingarrangements.com.au.

The District Court was told they then met on a number of occasions and were intimate, however he did not tell her he had a wife and children.

It was not until she was scrolling through social media and saw a photo of him with a public figure, while wearing a wedding ring, that she discovered he was married.

The court heard she confronted the man, referred to only as "RJ", but he claimed he was going to leave his wife.

Accused 'ghosted' by former lover

Roche's lawyer, Linda Black, told the court, a short time later the man "ghosted" her client, cutting her off from any phone or email communication.

Ms Black said Roche felt "betrayed and devastated" and it was in that context in early January 2020, over a four-day period, she sent him nine emails demanding he pay her $150,000 in cash or she would tell his wife and business associates about the affair.

She also demanded he pay her $50,000 a day if the demand was not met by a certain date.

The man reported the matter to the police and Roche was charged with extortion — a charge to which she pleaded guilty just a month before she was due to stand trial.

A victim impact statement was provided to the court, in which the man detailed the distress Roche's crime had caused him and his family, including the financial cost of hiring a law firm to get his name suppressed.

'He brought some of that on himself': Defence

Ms Black said while Roche fully accepted her conduct was "utterly wrong and unlawful" the man also had to take some responsibility for "cheating on his wife and pretending he was not married".

"He brought some of that on himself to some extent. He chose to act that way." Ms Black submitted.

The court was told that at the time Roche sent the emails she was also unwell, from what she wrongly thought was a sexually transmitted disease she had contracted from him.

"She was devastated because she thought she had found a relationship with someone who was available … she's then scrolling through social media to see the man she really loves with a wedding ring on his finger."

" … she was broken, devastated and angry. [That] caused her to behave in a way that was criminal.

"She went through a phase of being furious with him, wanting to punish him."

Elements of 'spite, vindictiveness' in behaviour

Prosecutor George Brett told the court the man had no recollection of any discussions or agreements with Roche about money.

However Ms Black maintained the man had said to Roche he could "help her towards getting a house".

Mr Brett submitted there were elements of "spite, vindictiveness and greed" in what Roche did.

He said she had threatened the man in three separate ways — firstly to tell his wife about their affair, secondly to harm him professionally and thirdly a veiled threat about making a complaint through the #metoo movement.

Ex-lover's actions give 'context' not 'excuse': Judge

Judge Fiona Vernon said while Roche's crime was not particularly sophisticated, it was persistent.

She also said that while Roche was suffering from elevated anxiety, stress, and depression she was capable of understanding that what she was doing was wrong.

"The discovery of his marital status … coupled with the ghosting of you caused you anger and distress."

"That provided the context of the offending … but it does not provide an excuse."

However, Judge Vernon accepted that Roche now had insight into the wrongfulness of her actions, and she said was a low risk of reoffending.

Judge Vernon imposed an 18-month jail term but suspended it for 18 months meaning if Roche commits any further crimes in that time, she is liable to be brought back to court and made to serve the prison term.