Is she molting? That would cause similar behavior, and a daily mist bath will help make her more comfortable. Most likely she doesn't have mites, although you take her outside sometimes if I remember right so it's theoretically possible for her to pick up parasites left behind by wild birds.
Here's a link on the types of mites that pet birds might get:
http://www.exoticpetvet.net/avian/mites.html The kind you should look for are red mites, which are detected by covering the cage with a white sheet at night and then checking the sheet in the morning for the presence of mites - they get on the bird at night then get off the bird in the morning. Bird lice are also a possibility, but they will usually make their presence known by damaging the feathers.
DO NOT get one of those store-bought mite protectors or mite sprays. They're ineffective against mites and aren't good for the bird. If she really does have mites she needs to see a vet and get a vet-prescribed medication.