I posted this in the general buzz forum as well, but here are more details on the accident:
The girl, Yoshino Kogawara, was 19. Her friend, a 20 year old, sitting directly behind her, is in critical condition with a head injury as well.
There are pics on Asahi.com of the wheel assembly from where it detached. This happened on the way down the hill towards the helix, right where the coaster gets most of its speed. The train was almost to the end of the ride, at the valley just after the upwards helix, and just prior to the final curve.
Fortunately, she was killed instantly, so there was no lying there, in pain. Again, it's all very sad.
You may not be able to read it, but here's the link to the Japanese paper, and its photos/drawings to help better explain the tragedy.
http://www.asahi.com/national/update/0505/OSK200705050005.html