My Grandma is driving me crazy!! Please help!?

I live with my late-80s year old grandmother. I moved in with her in August of 2010 to save money by not living in the college dorms and to save on food costs. She has lived alone for quite some time as Grandpa died before I was born. However, she has always harped on me telling me I'm lazy, or she always wants to go places when I would rather stay home and relax after my cles. She always has me drive places for her, and when I'm gone just a few minutes over the time I say I'm going to be back, she goes crazy calling me and asking where I am, and if I don't answer (because I'm driving or taking a test or something) she tries to call other people to find out where I am or threatening to call police if I did not call back (yes, she actually threatened this while I was taking a very important college exam even though I told her the time I would be home, but she called half an hour before that time). She always complains to me about my parents and stuff they do and she really has a thing against my dad for some reason. My parents got me a ceramic space heater about two weeks ago because my room gets super cold (like having to wear a heavy coat and thick socks to even think about being warm) even when the thermostat is set to 77 degrees. She keeps the TV on really loud (like max) so I keep my door closed so I don't have to listen to her tv she has on constantly. And she doesn't like that and lets me know by yelling at me about it (and yells at me for lots of other reasons). She has recently been complaining non-stop about this space heater, and how she thinks it will cause her house to catch on fire, and she always comes in to check to see if I unplug it at night (which I do because I know how to handle a space heater). I am taking all the precautions to guard against fire, but she still does not trust me. She does not believe in privacy either and wants everything her way. Yes, it's her house, but she has to learn to live with people and know that I have my needs too. What can I do to make her stop disrespecting me and my property and how can I learn to tolerate this?