She hid her disappointment. Not that she wanted rain -- but rather than react to her situation she made a plan (to follow Thranduil's advice) and hoped for the situation to bend itself to that plan. A very narrow-minded view of action, to be certain. But Sansa thought it was at least one step in the proper direction.

"Maybe if I whistle, she'll come--" her attention slewed back to Nymeria, and how Gendry rightly wanted to wait for the wolf to return before moving on. It was wholly possible that she was their best shield. "May I? Whistle?