It sounds like a difficult situation. I'm sure your girlfriend is very upset and frustrated by the experience.
If there was an unsatisfied lien from the prior transaction, your best option would be to sue the seller. That is, if you were sold the car while it still had a lien in place.
On the other hand, if the lien was satisfied at the time of the auction, you may be able to sue the lender for a wrongful repossession. If you would like us to evaluate if we can help, please call us at (303) 688-0944.