Just some background FYI:-
It is a well established fact with charter crews that if you visit the terminal to shop, you must get back in good time, or you may be left behind. There is no surprise that this has happened, everybody knows the score!
It is possible that the CC involved will now face disciplinary action from her employer - for failing to make herself available for a duty. This could theoretically result in dismissal.
It is well known that PMi is a large an busy airport where access to the aircraft is controlled and sometimes difficult - in short, it is one of the sillier places to go shopping!
Provided the legal number of crew are retained on board, pax may be boarded and the flight departed correctly, as was obviously the case here.
Waiting, even 5 minutes, could jeopardise the slot and incur a multi-hour delay (mentioned previously). This would affect not only pax on that partciular flight, but also pax on all subsequent rotations of that aircraft on that day.
If a person is old enough to initiate and manage an evacuation, then they are also old enough to get themselves back to the aircraft in time, or back to the UK from Pmi. If you don't like that risk, then don't do the shopping!
This person has my sympathy, because they're probably feeling extremely uncomfortable at the moment, but it was their own stupid fault - all this to save pennies on some fags/perfume/booze or whatever. The operation comes first - end of story - and we all know that!