The one thing I'll give this sharp change of event is that they didn't have a fight, which usually happens before something tragic happens, and that it's sort of hard to foreshadow a fuckin truck hitting someone.
But, truck and stuff aside, who was the original human that our parfrait angel fell in love with to turn human? And how did this happen? Was she born to humans, and if so, what was the plan to meet the loved person? Or did she just fall in love with the idea of humanity?