i am responsible for the loan and the car is titled to me.
Love made me do some dumb things
There are legal issues here, and moral issues here.
Legally, its your car. You can report it stolen if she won't turn it over to you.
Morally, it could be a different matter. If her car, as a trade in, was the down payment and she has made all of the payments since, then morally its her car.
Then, we go back to legal. If she can demonstrate that there was a "contract" between you and she for you to be a secondary finance person for the car and she is living up to the terms of that "contract" then a judge could rule that its her car...or rule that you have to reimburse her for the down payment and any payments she has made since.
Which is all a prime example of why people should NOT do what you have done.
I cosigned for a car for a roommate about 30 years ago (arg that makes me old) I ended up being the primary borrower because the dealership insisted upon it. I was young and had no concept of what I was doing. I do remember the dealer saying that I was "gold" so I had to be first, but I didn't understand what that meant. A couple of year later I got married and moved out, without even thinking about the fact that I had cosigned for that loan.
Luckily my former roommate was a responsible person and paid the payments responsibly, so it didn't effect my credit. I didn't even realize how seriously I was connected to that car until quite a few years later the former roommate got in touch with me because they needed my signature to sell the car.
So...people reading this thread, please understand that cosigning something is a really serious issue....married or not.