As long as the food is readily available, she will probably start to eat on her own(maybe before 72 hours)-until then I wouldn't worry.
If she is running around and seems strong, she should be fine until she figures out the food thing.
Here's hoping you get some more new babies to keep her...
That's correct. After that time, you may need to mix a little yogurt with her chick start or mash up a boiled egg to entice her to eat if she is a bit resistant.
I would say as long as mom is taking care of her and she is safe and eating and drinking, I'd leave her(may just go give her beak a little dunk to show her how to drink).
Hope your new baby does well!