Link had been staying very silent, moving slowly as he put first the Great Eagle Bow, then the Lightscale Trident into the Slate, doing his best to not startle Sophie with a sudden noise. And just keep her from noticing him in general; she didn't need to know she had an audience to her obvious borderline panic attack.
His first internal reaction was to see only Zelda and the very beautiful dress that would look very nice on her, and smile, and he struggled to keep that smile as relaxed and natural as possible, extremely aware of how tight of a rope he was walking on to keep from making Sophie's anxiety worse; too 'loud' of a reaction- verbal or silent -could potentially trigger a full-blown meltdown, but showing anything that could be misconstrued as insincerity could cause the same.
So he decided to just go with his first reaction, pretending to tune out Sophie's obvious distress and not make an issue of it.
"It was made for a queen," he said with a warm smile. "And a queen will more than do it justice." He looked at Sophie, still taking great caution about how he addressed her. He knew that his presence alone was probably making her nervous; she always seemed a bit on edge around men in general, and he was not only a man, he was a nigh-stranger, compared to the others in the village. "She couldn't ask for a better seamstress. You do good work. Thank you for this."