Perhaps the crew could ask for the police to confirm the passengers ATPL status. If the passenger is not a qualified pilot, then they have no right ro comment. After all, when was the last time a patient told a heart surgeon which way to cut?
There has to be some reasonable evidence for the police to progress in this way and the word of an unqualified layperson is certainly not reasonable grounds. I would be consulting my solicitor to sue the passenger if that had been me. Got to be some axe to grind by this woman.