How do I get my mother to give me the freedom I deserve and treat me my age?

Hi. I am 21 and currently live with my mother. Now most of you saw the question and think "Well it's simple stupid...move out!" Well, I don't have the money yet to move out (yes I do have a job), I don't have a car (I have insurance but it's on my brother's car) so I can't just move with roommates cause you still have to pay rent and also, no ride to get to work or other places cause they have their own things to do or don't have cars either. So moving out is out of the question. Like I said, my mother doesn't treat me 21 and doesn't give me freedom. I am only allowed to go out maybe 2 or 3 weekends out of the month as long as it's with my older brother or younger sister and I am not allowed to go to clubs or anywhere further than a 10 mile radius of my home or stay out past 2am. I can't sleep over friend's places, can't go out with certain friends, can't go out with guys she doesn't approve of (which is like all the guys I have ever met cause she likes to look for the simplest flaw in them), etc. The best of it all is that...I AM IN THE ARMY! I have been in the national guard for 2 years. I think I can take care of myself! I don't do drugs, I am a social drinker, I am a good person in general. Yes, I argue with her about things we might disagree on, but I don't curse her out, I don't just walk out and do what I want when she tells me not to. And plenty of people tell me I am a better daughter than most girls/woman they have met. I have a seasonal job at Victoria's Secret, I start college in January and I plan on getting a cl "D" security license so that I can get a part time job as security while I study. I help her around the house with chores and cooking, help her take care of my 11 year old sister. I am always buying things for my mother and sister even when I don't have much money to spend, I don't go around opening my legs to every guy I know (in fact, I am not ashamed to say, I have been a whole year with out being intimate with any one). So what do I need to do?! I know she is controlling but this has to stop some how. I could have had my own home about a year ago and a car but I was living with my father and I gave that up because I moved back with my mother after I found out she has cancer. I took care of her, my sister, her boyfriend and the house when she was doing chemotherapy. I have tried to talk to her but she always has an excuse. Either "The world is a bad place" or something like "When you're my age, you'll understand.", etc. So please, if anyone has any type of advice, please let me know. My ears are open for suggestions and opinions. Thank you!