Wait, are you that guy who had a psycho clingy emotional wreck for a girlfriend and didn't know how to get out of it? I can't remember. But if that's you, you've got nothing to feel bad or confused about, if anything you should have broken up with her and then driven her to an asylum and left her there.
If not...well, like Ciel said, you need time out from her in all respects. She doesn't sound like she's over you. So if you continue this way she's going to have a meltdown and try to claw you back and you sound like you don't want that. You might find it helpful to distance yourself from her in general, stop driving around with her and buying her things and all of that. Treat her like a lesser acquaintance, one you'd talk to but wouldn't necessarily do things with outside of uni or whatever.