That is strange looking--smart to take her to the vet.
How old is she?
I honestly am not sure what this could be without more information.
If it is PBFD (circovirus), there are generally a few manifestations--- one that impacts young birds (which tends to be pretty aggressive) and one that impacts older birds (which often can go on for years)...same virus---just different impact based on bird's immune response/exposure age etc.
To test for PBFD, they will generally do a blood-test in multi-bird homes. A feather test is available, but it can be even less accurate.
Do you have other birds?
If so, you will want to get them tested IF this is confirmed to be PBFD. If this bird has it, your other birds could be carriers, even if they test negative (it's hard to test for unless a bird is actively showing symptoms). A carrier bird can spread the virus without showing symptoms and without testing positive...so I would just keep that in mind if you have multiple birds-- especially when it comes to situations where they could spread the virus outside of your home.
It could also be plucking, parasites, polyomavirus
I would DEFINITELY get your bird tested for polyoma is you haven't (sometimes called "french molt virus").