Deconstructed: Virginia doesn't mean to be stupid. In fact, she's not stupid, just naive. Maybe it's due to Values Dissonance if she's in a different time and place than she usually is. Maybe it's due to her previously sheltered existence. Or maybe she's just under so much pressure being the MacGuffin Girl, Barrier Maiden, Miko, Queen of Somewheria, etc. that her nerves prevent her from thinking clearly; she's so worried about messing up that she ends up doing stupid things.
Reconstructed: But, she learns from her mistakes, and becomes a more mature and wise person. She also learns what's acceptable and what's not for the culture she's in. And she gains more confidence and is able to fulfill her role more effectively.
Played For Laughs: The wielder of the Virgin Power is male, and tries (and fails) desperately to prove his manhood, even at the cost of his powers. Hilarity ensues.