As much as she will drink. I've been using a 1ml syringe and give at least 4 full ones at a time, until she doesn't want to drink anymore, and I've been doing that since 8 am. I've since gotten her to eat a tiny bit of plain Greek yogurt, and had my husband get colace gel capsules. I just don't know how to administer them to a chicken.
So how much fluid do you think is in her crop right now? FYI, when i have one that does not have crop clearing issues, it gets 15ml per pound several times a day.
The Colace (DSS) gel caps can be given orally. Do double check that the Colace has just DSS, you do not want to give the one that also has the stimulant.