Is OTHER wrong in the post ? POST : I know this isn't a sub for relationships but what I'm talking about isnt really about the relationship.

So I split from my gf around 6 months ago dont really need to give more information than that but it absolutley broke me. We lived together and shared a car which is on finance and we both paid for out of a joint account.

So, we both moved back into parents houses etc. And as the car was registered and the finance was in my name I kept the car to which she agreed.

Roll on a few weeks and I get a text from her asking for the money that she paid for the car. I had recently found out that she had cheated on me from a very reliable source (she doesn't know that I know). I told her I'm not giving her anything because legally I don't have to, plus when we had the car she used it way more than I did, she would drop me off at work and I would then get a lift home from a work colleague. She was also really bad with money and would only put £20-30 of fuel in a month whereas I would put that in per week, I also paid for all of our food shopping whilst she was spending her wages on stuff that wasn't needed i.e clothes, makeup etc. I did pull her up on this and she said I didn't have to which I found very selfish of her when I spent a lot of money to make sure we had everything we needed and I was really struggling to make ends meet. 

Anyway, she asked for the car money and I said no I don't have to pay you anything and explained my point to her, which then led to a series of abusive texts on her behalf.

TL;DR- AITA for not giving my ex any money from the car we both paid for even though it's in my name?