“…..committee decided to delegate the strata manager to represent them at mediation (after she explicitly said that’s not in the agreement – she charged $180 for the pleasure)”
Most committees choose the manager to represent them because doing so saves the committee members the shame of demonstrating their incompetence or ignorance of their responsibilities in front of the mediator.
“…the attitude and demeanour of said strata manger during the discussion – sarcastic, contemptuous, utterly non conciliatory, IMO totally unprofessional”.
I assume the manager’s poor behaviour is aimed at you and not all owners. If so, I recommend you not complain to her boss as the first step. Instead I suggest you make a formal complaint to those the manager works for ie the committee. Write to the committee informing them of the poor behaviour, abuse etc that you are enduring from their appointed manager, who it seems is treating you as instructed by the committee and that you have had enough.