Since she has not fully paid you and you continue to have title to the truck then you continue to retain ownership rights.
She obviously knows that you are still the owner of the truck because you continue to have title and she owes you a large amount of money.
After 2 years it does not appear likely that she is planning on paying you the balance of what she owes you. $15,000 is a large sum and, if she can get away with it, she probably feels that she purchased a $35K truck for only $20K and since 2 years has passed, you have no intent on chasing her for the balance owed. Some people just do not have any scruples.
It has come down to the time when you must take some type of action, otherwise you will never see your $15,000. nor the truck for that matter.
Your options are as follows: 1. sue her and get a money award for $15K plus interest which you may never collect on; 2. sue her for return of your truck, but the Court
may require that you return a portion of the $20K that you received from her; 3. Since you continue to have title, repo the vehicle on your own and retain the $20K as your fees to use your truck for 2 years and for damages to your truck that she surely has inflicted after 2 years use. If she comes up with the balance due, than you may decide to transfer ownership over to her.
If I were in your shoes I would probably go with option number 3. This option gives you the truck and $20K, with the probability of her coming up with the $15K balance.
Hopefully you retained a spare key. One morning she may wake up and find that your truck is no longer parked in her driveway.
As always, you should consult with an attorney in your area that will provide you with legal advice concerning these options and maybe additional options.
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