CaptPlayStation
In my time there, it was rare for flights to be cancelled for frivolous reasons. In fact, it never occurred to my knowledge.
There must have been an operational reason.
There was, I believe, a small event involving a BBU based aircraft a few weeks ago. I'm not sure if the knock on from that event may have impacted your wifes flight.
Google Wizz Air and click the news icon. It'll tell you the event and date therein.