I would imagine that's she is just confused and scared from being re homes so many times, poor girl. I really do hope that you work with her and please do not send her away for the 5th time.
Keep working with her with the metal cage. From my experience training my four I've learned that they are the most efficient and safe way to train them. You could use the one you have as long as she isn't going potty in it. That would sort of defeat the whole idea of cage training.