Why is it staggeringly arrogant? I have been there. Not in this situation precisely, but I have been there.
It was either mental health issues, or a gross and completely un-necessary overreaction that has perhaps scarred permanently the life of the truck driver who hit her. Which one of those is more polite to say?
There is no reason for anyone to kill themselves over this. An appeal to her local council would have seen them almost certainly give her the money she needed. That she did not means that this possibility did not occur to her, or she chose not to pursue it. Were she otherwise mentally healthy, this beggars belief. Take your own life without exploring other options? With mental health issues underlying, though, it's completely understandable. I almost destroyed my life for the same reasons, failing even to contemplate the idea that there might be someone to help. And, yes I was mentally ill at the time. I am speaking from experience, not from arrogance.