Are you sure she's not over-grooming herself??? It sounds like feather destructive behavior to me, but would like to see photos of her.
Eclectus and Psittacula (Asian ringnecks) are the two species most notable for having bad molts, to the point that they do have grey spots and they just look a mess. However, after about a month or so, after the feathers have grown back in, these patches of feathers fill out and they look gorgeous again!
Typically, in any other species, it's often a sign of plucking, snipping/clipping, or some form of over-grooming.
ATM, I only have one conure that has a grey patch of feathers where her green ones are missing... however, this is due to an attack by another conure before I got her, and those feathers have not grown out yet. Well, she's gotten one, which resulted in that one feather sticking straight up rather than laying down cause it was right in the middle of the patch... lol