Second incident of its kind in one year. A quadraplegic man fell out if a tandem harness earlier. That incident had to do with hypermobility and a tandem masters decision to go along with no tying the passenger's legs to his own (on the passenger's request).
This one is being discussed at dropzone.com. Seems like an improperly tightened harness or a tandem jump with someone who shouldn't have jumped. Short (5 2) woman with lots of weight (220). With tandems becoming so mainsteram, there's talk of negligence and improper procedures, although there are not enough information out there to know anything, just speculation.
There is in tandem harnesses the same weakness as in sport rigs. It's known as "The Hole" and is basically where your butt is. In short, articulated harnesses it is quite possible to fall out of your rig, even if it is donned correctly. The legstraps may move in certain positions (such as in head up flying), creating enough room for the rest of the body to wiggle through if some countermeasures aren't taken. Freefliers (people predominantly flying head up, head down and making lots of transitions) usually have installed a small short cord between the leg straps to prevent this. Some harness manufacturers have adressed this with socalled "Fancy pants" which have elastic webbing integrated with the leg straps as a fix.
In short, this shouldn't have happened. I'll be sure to follow up on the discussion to get info on how and why it did.
Dropzone.com has a Incidents forum. Anyone involved with potentially dangerous jobs or hobbies normally understands the importance of discussing fatalities - to learn from them. Discussing fatalities is more than just morbid curiosity. It's pretty much essential if one wants to minimize accidents, incidents and so forth. Not pretty reading, not fun reading at all. I get a big "oh no" feeling when I see there's a new thread in Incidents.
The woman probably fell from around 5500 feet - the normal deployment altitude for a tandem jump.