Car doesn't look badly damaged, the impact seems very minimal - there has been worse accidents in worse cars with little or no injuries.

Possible reasons for such a serious outcome:
1. Didn't wear seat belt or seat belt faulty
2. Takata airbag faulty, didn't send back for recall
3. Intoxicated - causes blood vessels to dilate, making blood loss worse

Not trying to pass judgement, I'm very sorry that she passed away. I'm trying to understand why someone can be fatally injured in what looks like a minor crash.

Looking at the interior, the place looks fairly intact. The steering looks like it has risen up a bit but doesn't look like it has come inwards towards the driver. Dashboard, A-Pillar - all looks normal.

Hard to say whether or not she was intoxicated, people like this may do singing gigs cafes and bars until late night - or she could just have been going somewhere for whatever reason. Don't tell me you have never in your life driven your car late at night for reasons other than being drunk? Kinda stupid right?