Bill of sale is pretty much useless. That is really only used to prove the price paid for the vehicle. I mean, sure, anything will help you at this point, but a bill of sale alone will not get a car registered right. Do you have her full name? Drivers License number? You need to report a fraudulent transaction to the police. I don't know what else you could do. The title is the MOST IMPORTANT part of a person to person car sale. No title, no deal.
I hope you didn't pay a lot for this VX!!! Good luck!
Vart