She will always be slowly filling up and you will have to drain her again. I have a hen with salpingitis, she's not acting lethargic or anything yet. Her abdomen is larger and she has a messy butt.
She has ascites. Ascites is usually a symptom of something else going on like a reproductive issue, cancer, and heart or liver issues. You can drain her abdomen to make her more comfortable because there is no cure for ascites unfortunately.