May Sei sense magic on your character? How much do you want him able to tell? Yep! He should be able to tell that Bryn's been touched by a deity and had some of that power left in her. I doubt he'd be able to tell WHAT she can do but he'd be able to sense she has some ability.

May he use this information to be a jerk to your character? Sure, why not.

May Sei's singing voice have a soothing effect on your character? How much? Bryn has no defense against stuff like this so...as much as he's trying for/capable of I suppose :|a Just clear it with me in advance before you do anything in case I might have a reason to not want her soothed.