Is it her breath that smells sour? I am wondering if there is a slight crop problem? If you have bathed her regularly it isn't that. All my birds have their own distinctive smell. Change up her diet and see if there is any change. Ensure there are plenty of natural and healthy foods, no artificial additives etc and see if things change.
I would definitely narrow down where the odor is coming from. If the 'sour' odor is coming from her mouth, I'd strongly advise you to seek out an avian vet as it could be signs of a crop infection.
If its her feathers, then it could be one of two things. It could be just her natural scent OR it could be an 'absorbed' scent from her environment.
For example, if Skittles takes his 'morning dump' inside his sleep cage, there is a STRONG odor and if he spends a significant time near it, his feathers will absorb the odor temporarily. He has done that a few times (done a morning dump in his sleep cage) but its when I've overslept. Normally, his morning dump is taken on one of his playstands (usually the one by the window).
As for natural scent, when I had my cockatiel, Peaches, she smelled like maple syrup and when she was wet- the smell was EXTREMELY potent and you could smell the 'maple' from several feet away.
Skittles breathe smells like 'cake mix' and its mostly due to his diet. When he regurgitates his food, it has a strong odor of raw cake mix and the scent just permeates through his feathers. As a result, he smells like cupcakes.
Thank you for the responses! Her breath is perfect, its definitely body odor. She is transitioning off of seed to Tops pellets nicely.
We eat breakfast together every morning, I'm her only friend so she wakes me up at 5:15 and is given a buffet of food:
veggies
pellet
Nutraberries
fresh sprouts
bean mixture I bought at the parrot store in my area and
half boiled egg shell on with the yoke scooped out (cholesterol). I change it up, but for the most part...
I love her just the way she is but if its a health issue I want to get on it right away.
Hun if you never give any egg yolk then there is a lot of nutrients missing. Cut the amount down, ie 20 min hard boiled but use an egg slicer and give a smaller portion. This is imho considerably better than feeding Nutriberries as part of their daily diet certainly at my last look at the ingredients.