Asked: Venting/Advice on dealing with an overbearing mother?

My mother is being extremely annoying and I guess I just need to vent and maybe get some advice on how to cope from people who know what Im about to say.
So Im 21 and the youngest in my family and the only one left at home with both parents. My brother got married over the weekend and my mom was being such a jerk to me the entire time even though I tried to avoid her (like I always do at family gatherings) and I didnt provoke her precisely because I know how she is in stressful situations or whenever someone doesnt do what she wants. Besides I didnt want to ruin my brothers wedding or let her kill my fun, even though she tried to embarrass me and was picking on me about stupid things and not even talking loud enough for me to hear when she snickered and said something about my outfit to my aunt. The following will probably sound stupid because its petty but maybe someone who has a parent like this will understand, a little while ago I was serving myself juice and while I was about to pour it she tried to take the gallon from my hands and I told her to hold on and she kind of raised her voice and said she wanted to serve herself and that she bought it anyway so I couldnt get mad. Couldnt she wait two seconds or at least ASK me to serve her a glass?! I didnt say anything but I got so annoyed and I just left the juice there with the cup and went into my bedroom. She does this type of thing all the time. Even if I get something like dinner or whatever and Im ready to sit and eat she tells me to get up and get her some too even though she knows she couldve asked me when I was in the kitchen or even gotten up to serve herself. She even has the nerve to do that after arguments and then TRIES to guilt me into doing something for her which doesnt work because I know shes trying to manipulate me. She acts so immature sometimes, like shell act like a kid and throw things (and then gets even more mad because she has to be the one to pick up whatever she threw) in a fit for any stupid little thing. Shes also always had a tendency to compare me and my siblings to others kids and she also criticizes everything because shes the type that thinks she could do everything better and even my dad has told her to her face that nothing anyone does is ever good enough for her which is why I usually never even show her what I create that I feel proud of because Ill admit that it hurts when your own parent tells you how it SHOULD be or that it could be better or that its just stupid. She frustrates me so much and I cry out of anger a lot because I just feel like exploding at her sometimes but I dont because I hate feeling like a drama queen and sometimes I just dont feel what shes doing at the moment is worth letting her know exactly what I feel because I know it would make her cry because I just hate her so much sometimes. My dad is great and Ive never fought with him because hes pretty straightforward and doesnt compare me to other people or expect me to be psychic and know what he wants nor does he treat me like a servant even though I do things for my dad BECAUSE I feel he deserves it. Respect is mutual as it should be and hes the person thats always made living at home bearable. Its my mom that gives me whiplash with her moodswings that I know she can control if she really wanted to but shed rather just act like a bratty toddler and start screaming if something doesnt go her way because she feels the need to control everything and everyone. She even TRIES to keep me from going out and is really nosey and acts like Ive behaved in a way that would be reason enough for her to not trust me! Like sometimes if Im on my computer or phone chatting with a friend or just giggling at something Im reading or watching online she tries to see what Im doing and gets mad when I tell her to leave me alone. I get extremely irritated at a lot of things that are usually caused by her but I can definitely handle myself so theres no reason why a woman twice my age doesnt even seem to try to. I know my dad gets annoyed too even though he doesnt show it much and they used to fight a lot because of how she is years ago when she was constantly fighting and spying on my brother who eventually left when he was old enough to. Sometimes I just feel like packing some clothes and heading anywhere but it would absolutely break my heart more than anything to leave my dad that way like when my brother left and my dad became depressed for a while because he knew he had been driven away and he didnt see him for several months. Besides, I definitely wont be able to afford living even modestly on my own dime for a couple more years anyway and I cant move in with anyone else because I dont want to be a burden and Im not close enough to anyone outside my immediate family to even consider living with.