Of course the vet would be best, but failing that drugs ending in 'azole' are all anti-fungal. And 'thrush' in chickens or humans is caused by the same fungus called candida albicans.Of course you can. See if the vet will prescribe fluconazole for her.
So the only question is safety (and secondarily dose).
I have no direct experience but if you look for posts from azygous here on BYC you will find an article on sour crop and other wisdom that reassures on the safety of human-use azole drugs in chickens. Dose is less precise because you basically just smear it all around!
You can also get an azole in a liquid formulation - used for ear infections and athletes foot. That might be better if her issue is mouth and ears - might just be easier to administer - but it is a much less common formulation than a cream so I don't know how easy it would be to find.