In NSW the sale of Common Property requires a unanimous resolution (100% in favour) by all Owners in attendance at a General Meeting, both in person and by proxy and including any that may be un-financial from a Strata perspective at the time of the vote.
A few additional points that may assist in your circumstances:
1) All Owners must be provided with the Meeting Agenda including all Motions under consideration and relevant supporting information at least 14 days in advance.
2) Any proxies held by the Strata Manager, Village Operator, or the Proponent cannot be exercised if any of them would receive a “material benefit” from the use of those votes.
3) I’m almost certain that under the provisions of the NSW Retirement Villages Act the Proponent is at their cost required to provide any Owner who requests it with access to independent legal advice in order to ensure that they’re fully aware of the Motion and of its implications (if any).