clearly you have some interest in it
because they can make you pay for a loan
you need to negotiate in a sensible way ( ha! there is someone splitting in my family and talking to them is like reading an AB post from a usual suspect - it doesnt even start off as semi-logical)
NOT paying when you split - easy the car gets taken from the girl and you get saddled with the remainder debt
PAYING for the car - you have a lever of "everyone can see I dont pay for a car I dont drive"
She has legal title and you have an equitable interest
Citizens advice may be able to help (tell you how to get out of this maze at least cost)
remember than the loan contributions are not necessarily an asset ( ha! hem hem) because you have had the use of the car for which there would be a charge. If the loan is greater than the book value then you are both screwed