Bro OP, it's probably your phone that she's tracking, not your car. It's a lot easier to track your phone because it's already got all the hardware on it to be tracked. Plus it's more "comprehensive" because you go everywhere with your phone but not necessarily with your car. There are heaps of apps and websites that offer this service.

One exception is maybe if you drive a Tesla. You can easily track your Tesla using the app.

That said, I don't think knowing how she's tracking you is going to help. All the best, bro!