So... P.A. to pax in terminal. "We are really sorry but your aircraft has two unserviceable seats. WE can cancel the flight (and subsequent ones) rebooking you days later, or we can operate the flight, as long as you promise not to take photos of friends etc appearing to be sitting in the seat."
What would your vote be? I would have offloaded anyone stupid enough to even sit down on seat with a sign saying DO NOT USE!
I presume she would have used a lav locked/labelled 'inop' as well?