What age is she? I'm not sure why she would be jumpy, but I would think either she can see something from her cage that scares her, or the room has too much commotion. Do you have any other pets that might be bothering her? Although I don't really see why this would happen all of a sudden. Mabye it's just a mood swing.
-You can search all day for something and never find it, only to see it in the most obvious of places after you've stopped looking.-