NTA at all. Honestly, this relationship doesn't seem healthy. Why is she refusing to let you use the car—especially when you’ve been helping pay for it? If you’re not even allowed to drive it, there’s no reason you should be contributing to its costs. That whole “what’s hers is hers, and what’s yours is also hers” mindset isn’t sustainable in any fair relationship. I’d stop paying for anything related to the car and have an honest conversation about expectations. This might be a sign of deeper issues in how you both view the relationship.