I know what you mean. I was telling my mom the other day that I wanted to go to college in San Francisco (an hour away from home but SF is urban compared to my suburban town) And then she asked me how I'd get to school each day because I'd have to drive through traffic each day. I was confused. My mom and I pictured two different things for college years. I've always imagined living on campus in a dorm while my mom pictured me living at home.
You should go out of town for school. You'll be an adult and you want to start your life, your future. Once you have your degree and have matured and become independent, your mom will see the importance of your choice.
You should probably have a good discussion with your mom before leaving to college. Write down your points beforehand as well as your support. You want to show your mom your determination to get your education. I am sure one she sees how much it truly means to you, she will be okay with you moving away.