Well hang in there Michelle. I think there are times when certain things can be attributed to plucking and feather chewing, but there are also times when it's just one of the birds' habits. We don't know why, but I'm hoping your vet can help rule out anything serious. She may just need something additional in her diet, or you may need to eliminate something.
If nothing comes back from a medical standpoint, you may need to look at her nutrition. Her little body might be better with a different type of pellet, or maybe her system doesn't handle much beta-carotene very well.
Just be patient and don't let her see your stress. I'm sure she'll be just fine
andrea