I agree that you need to get your degree. No question about that. But you are 21 years old. There are other ways to continue your education. You could get a part time job. My daughter is in college and does a lot of baby sitting. She also has worked at Starbucks and Chik-fil-a while she's been in school. She also has worked at a horseback riding camp. My high school age daughter is 15 and she will be working as a lifeguard this summer. My son has worked at Subway and Texas Roadhouse while being in school. My nephew works on campus at the University of GA and my other nephew works at a grocery store.
You can get student loans and Pell grants that don't have to be paid back if you declare yourself independent from your mother. Obama has just increased the availability of both of these options.
The financial aid office of your college can help you with all of this.
You can find places to live that are cheap if you look. I currently own a house that I am looking to rent out for just a little over the cost of the utilities. What about living with one of your siblings? Or would you consider living with your boyfriend?
You, at 21 years old, do not need to be dependent on your mother either financially or emotionally. You are making that choice yourself. It's time to look after yourself and make decisions about the course of your own life.