Miss Gilbert is a Timneh and they tend to be smaller. My Grey is a Congo and she's a big girl yet she's never broken 490 grams. She's typically 460 grams but she's a female.
Some people freak out when they can feel the keel bone. This is normal, even more so in birds that are not flighted. My girl is a constant flier and she still has a very noticeable keel bone.
Question about your vet, which I may have missed: is this an actual avian vet? I know it can be hard to find avian vets.