Bankruptcy Law Questions? Ask a Bankruptcy Lawyer.
You need to execute a vehicle promissory note to your mother for the amount she loaned you and take that to your county tax office and ask for this lien to be added to the vehicle's title. You can find a promissory note online - just "google" it.
So long as the lien is an honest one - in that you're paying her back and can prove it - it should protect the vehicle.