I would highly recommend a complete blood count and a chemistry panel. If her stool isn't abnormal there probably won't be anything of note on it. Some people recommend probiotics for birds, but I don't believe there's any good evidence that what we have on the market right now works for every companion parrot. Not because they're bad products but because there is such a diverse group of species.
An x-ray is definitely not a bad idea, they do have to be anesthetized for it though. Not that it should deter you, but you should be aware. Anesthesia (when there is knowledgable staff) is generally a very safe thing for x-rays, it's brief and for the bird's safety as well.
While you're waiting for your recheck, just get to know your new little one. If you know that "she" is for sure a "she" watch out for nesting behavior that you can discourage, and you can start offering her new foods in different ways. Don't be afraid to try the fruit zupreem first and then work in the natural colored pellets. She's had 15 years to eat garbage and so at this point any pellet is going to be an improvement!