100% the car driver’s fault, imo.
Total negligence on her part.
Not even a doubt in my mind.
Funny thing is, I actually feel bad for her, too. I’m sure she didn’t anticipate that this would result from her actions. She was motivated by good intentions. I imagine she probably feels terrible about the deaths that she caused (or at least contributed to), and won’t ever do something like this again. OTOH, one of the reason we punish people for criminal acts is as deterrence, so a suitable sentence here to remind people of the possible consequences is necessary.