Ceria merely stands held in place, enraptured by the tiefling's tail via the musical spell.  She flinches when one guard yells something about an illusion, but cannot seem to look away or remember where she is or what she was doing.  The blush is gone and the elf's eyes are glazed over.  A listless smile sets upon her lips;  the expression almost perfectly matching that of the equally enraptured guard. 

Suddenly, Ceria heard at least one sword being drawn.  The scrape of metal leaving scabbard wakes her to full alertness.  Whipping her bow off her back, Ceria has an arrow nocked but the bow pointed down at the ground as she whirls to observe the spectacle.  However, what she sees doesn't seem to make much sense given that the enchanting song has made her feel oddly fuzzy and befuddled (befuzzled if you will).  Her face has returned to its usual serious expression, something very close to a killing calm (though not quite since Ceria had never killed another sentient being that was not possessed or transformed in some grotesque fashion).