You might consider sending her for an autopsy. It will give you some piece of mind and help you treat or prepare in case another chicken starts showing these same symptoms. DON'T USE PURDUE!!!! I've done them through both Purdue and the University of Missouri (Springfield I believe). It is much cheaper through the University of Missouri (Less than $50 if I remember correctly) and they turned results around very fast. Purdue was a nightmare and 3x the cost.
Just something to consider!