keep going with the vinegar water for at least 7 days, then make a weaker solution to give all your chicks all the time to prevent this again. If she is pooping, pecking and acting more feisty, then she may be ok soon. Just make sure she drinks enough to stay hydrated and doesn't eat anything that's not soft and easy to digest for several days. You can soak her crumbles in water to soften them, but don't give her that for a day or two. Keep with the egg, yogurt, baby food and vinegar water, and maybe a bite or two of oily bread.