I doubt it was murder murder, there was no attempt to hide the body. These were all room mates, what most likely happened is that there was some sort of argument and they kicked her out of the car. At this time of the year in most places in Canada if you are lightly dressed you would die of exposure pretty quickly. The other two probably didn't know exactly what happened to her, and the police found the body after they explained what happened. They would have just gone to where she had been left, and the body would not have been too far from there.
It's no excuse though, here in Canada we understand what winter means and the consequences of doing something like that. From a legal point of view it would be regarded as reckless endangerment resulting in death, and that would result in a homicide charge. LE would have known what being abandoned in the cold meant, so there would have been zero sympathy for these two from them.
Something similar happened here in BC the other day, there was a house party where one of the guests was intoxicated and became belligerent, which resulted in the other people at the party kicking him out. Unfortunately he was drunk, lightly dressed with no shoes, so he was found outside the next day frozen to death. IIRC there were no charges placed since it did not appear to be a deliberate act.
