I told my mom I wanted to move out, and she told me I was stupid?

It depends on whether you are talking about finances only, or not.

Financially, it is stupid. Financially, the cost of moving out will FAR outweigh the cost of driving to campus... Weigh the cost of the car, gas, the wear on both the car and the tires, the insurance, and necessary maintenance, like oil changes... against the cost of rent, utilities, laundry costs, renter's insurance, furnishings, cable/Internet, groceries, and the labor of maintaining an apartment (cleaning, laundry, grocery shopping, etc.). Furthermore, the cost of driving to campus can be mitigated by arranging your classes so that you normally only drive to campus 2 or 3 days per week. Therefore, it is FAR more cost-effective to live at home.

However, most people your age are also eager to try living on their own, and experience a certain degree of independence. Those are factors that, to you, along with the convenience of living near campus, outweigh the financial considerations.

Your mother is probably also worried about you being away from your support network.

Can you compromise and live in a dorm on campus, walking back and forth to classes, saving the expense of a car? (That's what I did; every two weeks, my parents picked me up on Friday for a weekend visit, then took me back to campus on Sunday.) Such a compromise would demonstrate to your parents that you are cognizant of the need to save money.

If you are determined to move out over your mother's objections, be sure you have figured out how you are going to support yourself.

You need to be living in dorms on campus. You are wasting vast amounts of time every day when you need to be doing school work, wasting gas, endangering your life being on the roads too much (especially if weather is a problem in your area). Roll out your budget figures, and convince mom you need to live on-campus, not commute that far.

Apparently your mother has a limited vocabulary and poor communication skills.
Look at this as a math problem. Most universities require freshmen and sophomore students who are not living at home to live on campus in the dorms. Find out what the cost is (minus your current commuting costs) and figure how you can pay for this.
Can you work a part-time job and cover the cost? (Keep in mind that the time you will save commuting will now be spent working.) Can you get grants or scholarship monies to cover the cost of the dorm? If you can't make the numbers work, then perhaps you should go ahead and get a part-time job while you are living at home, and save the money toward moving to campus (or an apartment) next year. The added benefit will be that you will be out of the house more. (Keep in mind, your primary duty/goal is to get the best education you can, so limit outside work hours to what you can manage leaving time to get all your school work done.)

maybe there are financial problems. Or she just doesn't want to let you go