According to El's Tweet after I inquired about Breanni and her possible clone, random NPC visitors visit the faire at different intervals. How fitting that Breanni's first stop is the petting zoo portion of the faire? :D
It's still a mystery how Breanni managed to travel to and from her store in Dalaran in a matter of moments! Part of me is convinced that she has clones of herself running around Azeroth, just waiting to infiltrate all the cities with an army of mini-pets. :P
Aaaa~and /end silliness. XD
UPDATE: According to this Petopia thread, if you stick around long enough while Breanni's NPC is visiting the petting zoo, you'll hear her comment on the animals! Remind me to hang around a bit longer next time.