If you can, talk to that vet.
Some thoughts. I'm not a medical professional so take this for what it's worth. I could be way off base with any of these.
Does she have grit? If she does not have grit to help her grind her food, her gizzard may really be impacted. Some smaller stuff can squeeze through, maybe, but some stuff could get stuck in there. If possible, you might try feeding her grit. Grit will not help an impacted crop, but it might an impacted gizzard.
Then to show how helpful I am, the opposite possibility. I've read where birds can scarf down so much sand and gravel that it can cause an impaction, crop or gizzard. That study was on emus but there was something in the article that it could happen to other birds. So maybe grit is not the answer but the problem?
The other thought and an even less pleasant one. Maybe she ate a small nail or something similar and it punctured the wall of her gizzard when she tried to grind it up.
I wish you luck. It's rough not knowing.