Why is my mom so mean for no reason?

She calls me dumb and annoying. Like if I am doing chores( which I do voluntarily with no reminders or rewards) and i don't know where something goes she says I am just dumb and will never be able to function in th real world etc etc. She does buy me stuff I want, but I don't really ask for much. When I was little and I would get a large amount of money and put it somewhere safe she would almost always come and take it when I was at school without even asking me. She would always say she needed it to pay bills or pay for a camp I was doing. After a while of her doing this I started to get annoyed and would tell her that she needed to ask for it and that she shouldn't take my money and she called me a spoiled brat. she doesn't take the money I earn though from working and babysitting though. I take care of the family cat, i wash dishes, and i clean when stuff needs it. The only thing i don't do is laundry and cooking. Still, my mom calls me a lazy pig. I think she is angry because she has this hormonal disorder. I can see how she would feel depressed about having it, but does she have to take it out on me? Is it normal for a mom to act this way?