Lydia will be in the tower closes to the east to south-east corner; with the sun as close to her back as possible. As the gate is on the south side and they are approaching more or less directly, I would assume that this is the south-east corner and she will be facing north west. IF she can pass along the number and details about weapons without revealing herself, she will. It may be a "Psst! 4 riders with bows and short swords."<br/><br/>She'll continue to keep an eye out for stragglers, but have an arrow noched and ready.