Yeah it’s kinda sour like stinky cheese/smelly feet kinda lol hard to pinpoint
O.k. Now, smell her breath really well - are you sure the smell is not coming from her breath/crop?
I know you looked inside the beak, but can you look one more time to see if there are any plagues or lesions - anything in the throat or stuck inside the "cheeks" or on the tongue.
Stinky cheese smell, I'm really leaning toward her having a sour crop even though the crop is emptying overnight, she could still have a bit of a yeast infection.