Sina is still cowering when the Iron Bull enters, and perhaps it's that she's already afraid of what Church will do, but having two large terrifying men alone in the tent with her is more than she can weather. She recognizes the qunari, but having only spoken to him once, she can't be certain he won't agree with Church and come after her too.
She clumsily crawls back towards her pillow and extends a frail hand, and the tent floor is abruptly torn by what appear to be roots growing upward in a feeble, makeshift wall between her and the other two. It only makes it a little past the mattress before the spell strength wanes, but she keeps trying to coax it further, shaking and sweating and with one hand pressed to her shard, as though that will lessen the pain.