After saying how silly she is, or just not acknowledge the "OMG! Monsters!" act...
Break into obedience mode. "WOoooOOoo...Where's your sit? GOOD! Where's your Down? Good! LET'S Heel! Yayyyyyy! Good girl!"
IME, this is the age where they start to get really suspicious of strangers. The age that both my Rotties started to bark the alarm when we were doing something like bending to get a glass out of the dishwasher and they couldn't see who we were.
When Alexa was about that age, we had some friends come over to watch "Drakula" you know, the big budget one made in the early 90's?
Well, she was sleeping soundly when the scene with the wolves startled her awake. She looked around the room and saw a stranger with a big puffy white face sitting on the couch.
OMG! Booowoooowoooowooooo!
As soon as Sherrie took the pillow away from her face that she was hiding behind cuz the movie was scaring the crap out of her...Alexa just felt silly.:o :D
Be more interesting than your surroundings and let her know that You're not concerned so why should she be?
Agility is a great idea too.