hmmm. . . . now, the bird maidens know it all. But they are careful to keep the others in ignorance, if only because they might want to get into fights, which strain the magic that keeps the magic hidden.
So -- how does she happen to happen on a troll?
hmmm. . . one think I know is that she'll be a girl, not a dove, because she knows of the possibility. But not, I think, a spy job. True, they monitor all the others to see if the spell needs reinforcement, but she's too young. Also, not suited for spying.