Yesterday QF 37 MEL-WLG was turned around about 40 minutes into the flight. A clearly very mentally unstable female passenger assaulted another passenger and had to be restrained by the crew. The flight returned to MEL where federal police boarded the plane and removed the by now hand cuffed woman. The flight was delayed 5 hours before a new plane and crew were provided.

While the in-flight crew behaved professionally and handled the situation well I have serious concerns about the ground crew. The woman was clearly - pardon the expression - a nut case. She had been walking about the departure lounge screaming and shouting about god and the internet and wifi. Instead of denying her boarding the ground crew - to my amazement - rushed her onboard the aircraft. It didn't take half a degree in psychiatry to see this woman was deranged and in need of mental health care. I was just waiting for the moment she would go off during the flight, and sure enough...
She should never have been allowed to board. A dangerous situation was created. A huge inconvenience was created for a lot of people (I missed my connection and had to stay overnight in WLG) - not to mention the cost to the airline.

So my real concern is with the ground crew.
Does anyone know what kind of training they get in spotting such passengers etc?

Has anyone had similar experience?