Feel her crop during the day, and at night and see if it's filling up and emptying
Antibiotics won't help. Does your feed store have sulfadimethoxine or sulmet?
It's hard to say what happened. I just had a chick who had a blockage somewhere and died. I think the only thing you can do is make sure they have food and water.
There's not enough information here, but I would say that she had a blockage of some kind. If the fluid smelled, it was probably sour crop. How old was she?