My mother is manipulative. Help?
So I have recently come to the conclusion that my mother is selfish and manipulative.
For a very, very long time, I have had a combination of admiration and pity for my mother. Admiration, because I always thought she was so strong and willing to step up and take charge where my father failed; and pity, because I felt bad that my dad was such a terrible husband and that all my mother's friends deserted her. As I've gotten older, I've come to realize that these things are not true. She talks down to my dad and treats him like he's stupid. She pitches fits and takes things personally when I don't take her advice on a situation.
As for her most recent offenses, she recently insisted on installing parental controls on my brother and sister's new laptops (they are 18 and 19, respectively) and demanded to know how much money I currently have in my bank accounts (I'm 20). She lied to my grandfather and told him that I needed $4,000 to help pay for an internship this summer, with the agreement being that I would get enough to pay off my internship (about $1,200) and she would get to keep the rest ($2,800).
Part of me feels obligated to put up with this, because I still live at home while attending university and she lets me live here rent-free and pays for my car insurance. On the other hand, I am nearly 21. I am, in fact, an adult, and I feel that she has no right to be prying into my personal finances, telling me how to spend my money, or spying on my online activity.
I'm at a loss of what to do. I feel like I should say something to her, but I also feel like it would just cause more problems and give her more reason to be angry with me. Any ideas? (Moving out is not an option. I'm unemployed at the moment.)