In my mind if someone deliberately overrides safety features, deliberately ignores safety instructions, and deliberately takes foolish risk the foreseeable consequences of those deliberate actions cannot be termed an accident.
The park and its owners must be held blameless in this tragedy. Some gold digging ambulance chaser will no doubt argue that the ride should have had tamper proof restraints. But people (especially those of intelligence as this woman obviously was despite her actions) will find a way to overcome obstacles to there desires.
This woman was seeking the ultimate thrill. She got it.
Cold hearted, I am; but, maybe the park should sue the deceased's estate for bring bad publicity on them.