I agree with the advice given. Look around for anything that might have been toxic that could have been ingested. I would also do the vitamin supplementing (B complex). I've had birds in molt have balance issues or walk like drunk, and B supplements have been effective many times. There is no downside to the vitamins, it won't do any harm, and may help. Since she has lost weight, she may possibly be ill with something that can't really be helped, or she may just be getting kept from feeders by other birds (this could contribute to deficiencies also). It may help to add some feeders and waterers, spread them around, so that more dominant birds don't keep the lower order birds away too much. Last thought is internal parasites. That could affect her absorption of nutrients. If you can get a fecal test done (not usually terribly expensive) that would rule that in or out as a possibility. If you don't have a vet that will run the test for you (it's the same test for all species) then there are mail in options. This is on amazon, many livestock suppliers also carry this, you can shop for the best price & shipping:
https://www.amazon.com/Reptiles-Rab...ywords=fecal+test&qid=1617731556&rdc=1&sr=8-4
https://www.amazon.com/Reptiles-Rab...ywords=fecal+test&qid=1617731556&rdc=1&sr=8-4