I've noticed that my juvenile beardie will get lazy and cranky when they shed. I think its the same with most bearded dragons because they get really itchy and annoyed when they start shedding.
She bearded on me yesterday morning because I woke her up on accident when cleaning around her tank. I think it could be just because of the shedding.
And if you have a lighting fixture and a basking bulb, and have been feeding her properly, she should be fine.