I sold a car, my customer signed a contract stating that we will remain the lien holder until the car is paid in full, I gave her the bill of sale to take to the DMV with my company listed as the lien holder she then filled out a new bill of sale which removed me as the lien holder and she now doesn't want to pay for the car, do I have grounds to sue her?
Yes, the customer's actions would be deemed to be fraudulent.
Of course. Next time follow proper DMV procedures to retain your title interest.
Not only fraudulent, but criminal - the rewritten bill of sale would be a forgery. Mr. Nelson is right about DMV procedures, however; what you did was procedurally wrong.