"This isn't funny," you meekly say, "and what's worse is I'm not even the right age for this."
It appears to be right upon closer look. Although you're in this ridiculously girl-ish dress, you're also a full-grown woman. The skirt barely goes over the knees and the stockings seem to be stretched as much as they can. Well you do look relatively cute, your full-grown body also has a strange form of attractiveness to it.
"This feels like some sick idea of a Halloween costume," you complain a little more. The cute voice eminating from your lips still ruins any attempt at sounding whiny.
"Gee, don't get so cranky, ya cutie!" The fairy dismisses your complaints with a giggle, "You're still a pretty girl. And oh, what's Halloween?"
You sigh, seems the fairy is either playing some sort of trick on you, or you're just being the victim of a rather ditzy fairy.