If you don't have a large syringe to draw the fluid from the hen, you should remove the syringe from the needle and expell the fluid from the syringe. Do not remove the needle each time you need to empty the syringe. Each time you puncture her skin/abdomen you create a new entry site for bacteria. Good luck with your hens.
What I have done with all the 3 hens that this has happen to is, I start feeding her plain yogurt with a tiny bit of calcium in it every day. Then I make a mash with her layer pellets add warm water the I add some molasses for energy. I also give her all the fruits she want and bread, it sounds like alot but it works for me every time. Good luck with your baby .