There is apparently a way to empty out there crop. If you could find out how, that might be a good idea. I would try the antibiotics. Keep giving her yogurt. check out this site. Its another forum similar to what you might be dealing with. See if they have good information in there that might help.
http://www.thepoultrysite.com/forums/showthread.php?p=3729#poststop
http://www.thepoultrysite.com/forums/showthread.php?p=3729#poststop