Thank you all of you, treatment starts tomorrow so once I've got a proper look at he area, I'll trim the feathers wash it, give it some Epsom salts to prevent straining when pooing. I'll get some thrush cream and apply it around the area, I'm going to feel so bad if I got my old chicken put to sleep when doing this could have saved her, I'm not trusting vets again
FYI: Epsom salts is used as a flush in chickens.