There really was no threat of anything other than discomfort for the rest of the passengers. I did leap over the seatbacks and seize her cane when she started beating the window with it in an attempt to escape -- at 35,000 feet -- but not for fear she'd cause any significant damage. I just thought that other passengers might be alarmed.

Service during the flight suffered as the cabin crew was short the one FA who was dedicated to calming the lady.

According to another passenger, the failures began while this lady was in line at the gate. She was accompanied by two younger men, apparently relatives, who seemed very eager to get her onto the plane. She was ranting while in the line, too. Dealing with psychotic people is something most folks never have to deal with, so I wasn't surprised that the gate agent went ahead and boarded her.