Can you describe what exactly she is doing? Is there anything unusual on her body or with the shape of her body? I think it is more likely a problem with water quality or some disease.
The only unusual behavior you can see when goldfish are ready to spawn is that males start chasing females like crazy, and afterward they will peck the eggs. If you just have one lonely female you will not see much change in her behavior.
Let me know as many details as you can and we will figure out what is going on.
