VIC Private messages shares by their party to my workplace

I had an argument with a friend over private messages about a non-work related matter, but we work together.
This conversation was shared to someone else without my consent or knowledge, who then passed it on to a fourth person. This forth person - who is not related to the conversation at all - works with myself and the person the conversation was originally with. The forth person has now made a complaint to management about me and this conversation.
Is this illegal or cyber bullying in anyway?

The messages were in response to asking person A to dinner with myself and another friend, person A saying they were busy, and then they went to dinner with someone else. It had happened the previous week also, so an argument arose about person A lying as to why they couldn’t come to dinner. None of which at happened at work or mentioned our work.

I was told by another employee about the complaint because the person who made the complaint - person C - had a private meeting last week with management and after, had told person A that they made the complaint. Person A then told another employee and so on.. I know it’s not exactly hard proof the conversation DID actually entail a complaint against myself, but if it were to have been a complaint about the conversation O had with person A, I just wanted to know if anything I should be aware of or if my privacy had been breached and so on.

I haven’t had management approach me about this as yet, and it has been over a week now, but they can be pretty lax with dealing with this type of issue.

Clancy said:

Did the private conversation take place during working hours? Because you have to consider that the other person is affected by what you say while they are at work, and while they are at work, their workplace rights are unlikely to be set aside simply because it is a 'private' conversation.

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The conversation took place out of work.

I have since sat down with management to talk about this upon my request to explain how I feel very uncomfortable at work knowing the person A has been telling multiple people about the conversation. It was made clear that the matter is not to be handled by work - and I don’t want it to be - but my manager told me he went to HR to ask what could be done.
So the person I originally had the conversation with hasn’t made complaint to HR and simply wants to move on with the situation, but multiple other parties outside of the conversation are trying to involve HR.
Is there anything I can do in terms of Fair work because I feel extremely targeted. Myself and person A BOTH had strong words with each other, but person A is only showing screen shots of my messages and playing the victim.