Since the cabin crew provided her with a meal and at no time did she become agitated, my contention is that there was no threat to the safety of the crew and passengers. Let's see what the lawyers think.
So prior to boarding the flight the mother withheld information and used it to get her own way.
The crew was clearly, in my view, correct in wondering what else may have been withheld and what other risks may be present.
One thing for certain had an incident occurred involving one or more other passengers the only common point would be blaming the airline.
Not the mother for failing to plan the journey to ensure zero risk to others!
(and if you read the initial quote , the mother is entitled to use the title Doctor, so could be classed as intelligent)