I don't think anyone's been 'blaming the motorist' - ie, saying it's her fault. On the contrary, there seems to be general agreement that however sad the upshot, the cyclist was clearly in the wrong. People are questioning her version of events - that she failed to stop, on account of she thought she'd hit an animal, saying it's hard to believe she was unaware she'd hit a person, and that she really ought, in those circumstances, to have stopped. I find that hard to disagree with, dark and isolated road or not.
I also share others' doubts about whether the police's reported comments were laudable - or even acceptable. I'm not saying she should be punished; just that praising someone for leaving the scene of an accident where someone was killed seems an odd thing to do and sets a pretty dubious precedent.