Are you 18? If you are 18, which I am assuming you are since you are planning on going to the dorms, then by all means, she cannot stop you from going to the dorm. I don't care what you have to do in order to make it happen, it'd be worth it. Is she overprotective enough that she won't let you have a job? (Some parents are that way, and parents like that are usually too overprotected/biased to even listen to you.) If you're allowed to have a job, get a job. Save up money so that you can stay on the dorms. It'll be a lot different, but for the better. Coming from an overprotective family, you'll probably be homesick for the first week, a lot. You'll probably ask yourself if you've made a mistake or if you should really be there. Don't. The time you spend away from overprotective parents is the key to taking a big step up in your life that they couldn't force themselves to give you. That way you'll be getting things done on your own time, you won't have to be questioned nor lectured when you are an adult and you are far capable of taking care of yourself. If you can't afford the dorms, take out a 2nd bank loan (assuming you already have a FAFSA loan).
I believe you when you say you've tried talking. I really dislike when people don't understand why talking doesn't do any good, because for those kind of parents, no, there is nothing you can do about it. No talking will get them to let you do what you need. You have to do everything for yourself and you won't be able to depend on them.
Another thing you should do is take your parents with you to meet the house leader of the dorms, learn all about it. Take a brochure of the college's dorms and show it to your parents, tell them what all it has, ect. Another thing that would really help is if you have any friends going to the same college as you, ROOM with them. On your dorm application, write their names down as preferred roommates. If your parents know you and your friends and if they trust your friends, tell them you'll be with them.