Legolas went from smitten to surprise when he heard Aragorn imply that he knew the girl that the young Elven Prince grew fond of. "You know of her?", that was strange. How did this Man come to know Yavanna? In truth, Legolas only learned of the princess from his father, though never got the chance to physically see her, or find out what she was like, in the flesh. Was Yavanna widely known to everyone? Was it because that they viewed her as one of the stars of Middle Earth? The Elven Prince may have just realized that it might be her purity that made her so well-known. Could that be why the enemy wanted to harm her? To claim her light?