Are you sure the vent isn't just swollen from her being constipated? If you've been cleaning it, it could have been irritated and baby chick vent tissue is very delicate and swells easily from irritation.
You need to do something about the constipation because when she tries to go, it's usually very painful. Olive oil or mineral oil is good. Since baby chicks don't know that oil isn't water, they will slurp up a good dose by just placing it under their beak. One good slup, and it should be enough to get things going.
Use coconut oil on the swollen vent if you have it. It's both antibiotic and will heal it and soothe it. Or better, if you're in a state where you're fortunate to have it legal, cannabis salve smoothed onto the vent will take down the swelling, relieve her pain, and get it healing fast.
