Elevated WBC can be a sign of disease but it can also be from stress which is normal considering she’s been to the vet twice in a short time. I’m not saying that it doesn’t mean that she’s fighting a disease but it isn’t necessarily proof of it. Usually dramatically elevated WBC is a sign of...
I looked it up more, it’s a sulfa drug, similar to SMZ TMP and treats a lot of the same things, coccidia as well as a lot of respiratory bacterial problems. I doubt it will treat gapeworm if by chance that’s what’s going on but it’s a decent antibiotic.
There’s no such thing as over sharing, the more information the better.
I would follow Miss Lydia’s advice and avoid using the lime for a bit. You might also switch to using pine wood shavings instead of straw.
If it’s possible I think you should take your goose to the more experienced vet...