Yes, there are several health issues that can cause this symptom. Just one being a neurological problem from a previous injury, poor diet, heavy metal ingestation and others. The only way to be sure is to get a check up with a true Avian vet. It's good you did not put her in with your others as any new bird coming into our homes should be quarantined a minimum of 30 days, as far from our resident birds as possible. If you have them in the same room though, they are not quarantined. However, I don't think you have a contagious situation. Of course the previous owner would claim ignorance, especially if she did something stupid or careless that led to the problem. Or, it could just be ignorance of the many toxins we must protect our birds from. I hope this helps. If not, let me know.