The order of the incident was fairly simple. The car began its ascent towards the top of the tower. About 20 feet or so off the ground one of the 2 cables on her car snapped (this model has two cables many others have more but are also later additions and taller heights). Once the cable snapped it wrapped itself around her lower leg and ankle.
As this is happening the car is continuing to be raised to the top of the tower using the second cable. The car reaches the top and releases as normal. Now when the car releases from the catch car, the cable stays at the top of the tower while the car free falls. As it drops the cable gets tight, legs are lifted up, I would imagine the girl slid down in the seat as her legs where pulled until she was stopped by the restraint. Then the feet are pulled off of her body by the stationary cable as the car continues its decent.
Since the incident all similar drop towers have added safety sensors for each cable. If at any time the sensors feel that one cable is no longer present the ride will stop. This would leave the riders stopped where they are on the tower, or in the SFKK case about 20 or so feet off the ground. They would then have to unwrap the cables from the girls legs and take them off the ride using a cherry picker or something.
Or if the second cable were to break, the car and the catch car would both fall and slow down during the breaks. The guests would be untangled and unloaded on the ground in that situation.
I think it is easy for Six Flags to put the blame on the ride not having an automatic shut down system in this situation. A cable snap is something that is bound to happen one way or another, and when thinking about what could go wrong I think this is the first place you would look. Also giving the company's track record with safety, and over looked scenarios ending very poorly, a lot of time in fatality, its easy for Six Flags to try and take this one off of them. Now in Intamin's defense, this kind of thing is such a freak accident that its hard to consider thinking of ideas to prevent it.
As long as Six Flags can prove they have done every thing to Intamin standard in terms of inspections, as well as state standard, this is sure to be passed to Intamin.