You simply don't understand the dynamics of the disruptive pax situation,
Oh I think we do, but I'm just pointing out that the terms and conditions of passage are a matter of contract law rather than criminal law. If the airline wishes to recover money by issuing an invoice (which is what the article says they did) and the woman declines to pay then their option is to resort to a civil court. Also any Ts&Cs would (in the context of a court action) be reviewable through the eyes of the unfair contract terms act. Many Ts&Cs contain terms which are either unenforceable in law or even in conflict with the law (like web-shops in the whose Ts&Cs say that the goods are your property as soon as they are despatched and that the seller is not responsible if the item doesn't get delivered). MAny Ts&Cs have non-sensical terms. For isntance the abstract someone posted previously gives the airline the right to do breath tests, but does not define a threshold above which they might refuse passage - so the passenger has no way of knowing how much alcohol they can drink in an airport environment which positively promotes drinking before flights - a court would toss this out in a few seconds.
I also suspect that an airline which banned someone from a flight and then cancelled their booking for anotyher in (say) six months' time (under those Ts&Cs) would have a very hard time avoiding refunding the ticket price - civil law usually only permits recovery of damage suffered and it would be very hard to show that the full ticket price was an unrecoverable loss - a small admin cost would be reasonable, but that's about it.
To sue they must enter the court "with clean hands" (ie be very sure that no actions on their part could reasonably be seen as provocation), and they must have taken all reasonable steps to mitigate the losses they are looking to recover.
If there were circumstances which might be seen as sufficient provocation then the airline is on a loser. If the passenger's behaviour was not (in the opinion of the judge) sufficiently disruptive as to make diversion to shannon essential for the safety of the aeroplane or the people on it then they are unlikely to be regarded as having mitigated their losses, so a court wouldn't award damages (or might award damages but wouldn't award costs). And the passenger would have every right to reference (maybe even with expert witnesses) the medical studies which have shown that the poor air quality in the cabin of airliners at altitude can induce aggressive behaviour, espcially in combination with the alcohol which the airline sells (or gives away) on the flight.
I see the matter has been referred to the criminal authorities. If she is convicted of an offence this will support the airline's case for civil damages, but if she isn't then it will make it very much harder.
Finally on the matter of no-fly lists. In the UK it would probably be legal for an airline to operate such a list provided they didn't put people on it "unreasonably" or "capriciously". But a cross-airline list operated without a statutory basis and without a robust system of checks, balances and appeals would almost certainly be seen as operating a cartel and could land the airlines in a whole dish of the smelly stuff.
€0.03 supplied,
PDR