I'm not familiar with vent gleet, there's probably an article on here that you can read through. If her skin is irritated, see if you can give her an Epsom salt bath. I feed my hens sour raw milk and whole milk yogurt with live cultures and also pumpkin or butternut squash to give them some...
I would boost her protein content, her skin looks pretty dry as well, and her bottom is inflamed. The skin shouldn't be red there. Does she have a cheesy smell? Like Cheetos?
Does she like tuna? Cooked beef or chicken? Plain yogurt with live cultures is also good for them.