You don't need to put the syringe in her mouth. If your mixture is liquid enough (like thinned cooked egg yolk) then you can just put a drop on the side of her beak right above the hinge of the jaw (do chickens have jaws?) Anyways, she will reflexively swallow it. Once they get the hang of eating, start thickening your mixture with more egg yolk and then later with crumbles until they are eating on their own. For my sick chick I used yogurt, vitamins, electrolytes, boiled egg yolk and broth from homemade chicken soup. The little girl turned around in 3 days. She was so weak and starved that her legs were sunken and all you could see the bones. She would not eat, would not open her eyes and was swaying as she could barely stand. Now she is bigger than her brooder mate and eats constantly. I wish you luck with your little one.