My take is:
- a sled will only make sense if the path is generally smooth, which may not have been the case. The path might've been too uneven w/lotsa underlying roots below w/c would make moving a sled hard -> potentially slowing them down; also, it can make it difficult to avoid sudden attacks *like what if the ground was hit or something popped up from below
- she has to conserve as much magic power as she can because they don't know what monsters they might encounter (case in point, the yeti). Unfortunately, her reserves are so low she probs didn't want to risk running out by continually using magic like that (albeit the amnt will be small. But doing it frequently & plenty enough will make her power run out eventually or too fast if they encounter problems)
What if we switch to ice powers? There is already snow all around.
If I was there in the snow and had the same powers as Shiori, wouldn't it make sense to use a door or two to make a snow sled? And with earth magic, she could continuously lift up the back edge to slide it forward, so no need for anyone to carry the ill.
PUT THOSE ONIONS AWAY!