Because of [i]magic.[/i]

Quinn can absorb kinetic energy and store it in her body as potential energy, before expending it somewhere else. But the sand [i]is[/i] in her suit and there is a suit between her hand and the sand. It can be passed off if she converts that energy towards her suit and directs it to the sand in her suit, but I don't think that's ever been established as within her capabilities. It's already been settled, I believe, as a "herself and her target" relationship with no dative subjects.