Welcome
500% agree with the vet because parrots will pick at an area if they are suffering internally (x-ray, gram-stain, blood work, etc).
How much sleep does she get nightly? 10 hours is the very bare minimum for proper immune health and hormone regulation (which regulates a bunch of stuff, including eggs, screaming, plucking over-preening, screaming, aggression etc)--- it's not the only cause of those behaviors, but you must (at very minimum) meet their basic biological need for a light cycle and sleep schedule at 10 -12 hours (again, it should not be any less than 10 on a regular basis).
How much time does she get out of the cage daily (whether or not you are interacting)?
How much time do you spend actually interacting with her outside cage?
Do you have a gram-scale to monitor her weight (that matters when it comes to eggs, as they can get egg-bound and require emergency intervention)
If you pet her, where do you pet? Head and neck only or you will sexually stimulate your bird.
It's normal for them to protect their babies etc...She's also in hyper-drive because you have her with a male with whom she mated....so that is why housing males and females is complicated, as is separating them. I wouldn't have started them together (unless it was a bonded/rescue situation) but not everyone will agree with me on that. Separating is a judgement call that can be both helpful and stressful (just depends).
Does she have any huts/tents/shadowy spaces (if so, remove them- they are dangerous for many reasons but they often trigger hormones which can manifest as anxiety, over-preening, plucking, screaming aggression etc). Never partially cover the cage during the day . Other shadowy spaces include, burrowed in human hair, under a table/furniture, in boxes, coconuts, hollows, under low shelves, in piles of paper, wandering among pillows/couch cushions, drawers, closets, cabinets, under shelving etc.
Do try for more veg than fruit. Fruit and seeds are high calorie and they can be too abundant in captivity..but do not cut her off (especially post-egg) as they need more nutrition before and after an egg, and because it sounds like she could lay again. Even if she weren't laying, parrots can starve to death if you change diet too quickly-- they can be picky. Repeated exposure and excessive waste come with the territory and you may need to present something new over 100 times before she actually tries it..so just try not to feel too guilty about throwing out wasted veg.
Make sure her cage is not at all shadowy. I hope you do not have a cage with a solid/shelf top (those are too dark).
Make sure she knows how to play with toys and if you get a new one, don't just shove it in the cage or it can scare them and cause anxiety.
Do you use key phrases with your bird to help her/ the rest of your flock anticipate what you are doing? If I am going to be gone for 1-3 or 4 hours, I say, "going to the store" and if it will be longer, I say "going to work". Whenever I do something that involves sounds or objects that could be frightening, I use phrases, like "sweeping the floor", "unloading the dishwasher", "taking out the trash" etc-- it may seem silly, but they learn these phrases and the more they can anticipate, the less anxious they feel....barring hormonal stimulation or health problems.
