I understand that anyone can attend an AGM unless a by-law states otherwise. Those who are not owners would need to provide their name to the Chairperson and/or Secretary prior to the meeting to enable their attendance to be recorded in the Minutes. Only an Owner or their authorised proxy is permitted to Vote.
The Chairperson should lay down at the beginning of the Meeting the rules about who is permitted to speak and ask questions . One of these rules could be, as suggested by Sir H, that only the proxy be permitted to speak on behalf of an owner but not a third person.
A useful link is here: https://www.lookupstrata.com.au/nsw-owners-corporation-proxies-participation-general-meetings/
There are various books that may assist the Chairperson in difficult Meetings as the Act is not overly helpful in this area:
Meeting Procedure Made Easy By David Julian Price. Published by Cascade Publishing.
Guide for Meetings and Organisations By N.E. Renton. Published by the Law Book Company
Joske’s Law and Procedure at Meetings in Australia By Eilis S Magner. Published by The Law Book Company