She'll be 4 in September.  When she is on her playstands, the slightest sudden noise... nothing she's never heard before... will send her bolting off her stand onto the floor or somewhere else.  I can sneeze or cough and she's off.  

If she were flighted, she'd be who-knows-where in the house.  Even when I'm carrying her, she seems ready to take off.  I'll cup my hand over her head if I think I'm going to have to chase her on the floor.  Are some birds just naturally skittish?  

Hmmmm. My sennie, who is usually very outgoing, can be skittish sometimes. Maybe she saw/heard something to make her think a predator is in the area and now she is on alert? Not sure on this one!

She only freaks out in her cage (as in the screaming alarm) when I suspect there is a predator outdoors.  But she doesn't thrash around the cage or try to get away.  As an example, I was carrying her this morning, and I bumped my shoulder into the corner of a wall.  Yep, off like a bat out of hell.

I would say that with mine, a sudden noise or change gets them all a-flutter. I think mine might bolt if I ran into a wall while walking <g> too, but of course I have never actually done that.

What seems skittish could just be her natural prediliction to react to potential prey. Also, this may be kicking in of late because she is maturing and it is summer and, well, you know how females are ...

It's possible, except that she's always been like this. I guess it's just her personality.

Sudden startles can send even the calmest bird into a frenzy. They're prey animals. Its just who she is. There are exercises/games/training you can do to desensitize her if you'd like to try and calm her behavior...just takes a bit of research, time and effort.

I'm happy to say that she seems to have relaxed considerably. She no longer flies off my hand when we approach the cage, or at any other time. I think maybe she was going through a phase or had been frightened, and it's pretty much worn off.