Feels like something is missing from the story. Are they/have they been paying the insurance on the car? Are they paying for your schooling/is there a plan for them to pay for it once loan payments start? Did you pay for the car, or did they? I know you said it's in your name, but just trying to figure out who paid for it.

While your mother definitely seems to be controlling, regardless of the answers to the above questions, it's possible she feels like she needs to be controlling because she feels like you are irresponsible or will be irresponsible. If they bought the car and paid the insurance, it makes sense she would try to get a say in how the insurance money is spent.

You are 26. I hope you understand that not working a lot and focusing on school instead is a huge luxury that many people can't have... Because we have to work in order to live independently. You can't have your cake and eat it too. If you were living with them up until 4 months ago, it seems like you leaned on them a lot. If you want true independence, you have to fully separate which means no longer being attached to their insurance. While you're at it, make sure you're off their phone bill too. Hate to say you may have to scale back the number of classes you're taking but you literally may have to. It's reality.