Why is my sister like this? and how can I change her behavior?

[Anonymous]

My older sister is very stingy to me. She gives some of my siblings money, food, and clothes. But when I asked her she doesn't want to give me, and always mad like she has favoritism. Most of the time she gives my other sister huge amout of money, I stopped asking her anything. I don't always ask I was just testing her if she will give me. I am living in her house because I'm currently college student ( and saving money) . I do the cooking, do the cleaning and most of the time I take care of her kids, but still not enough for her. She is making me a slave. She always expects me to do her nails. She always bring me down, calling me names like retarded, stupid, bitch, dumb. She even accused me of stealing her foods, and accusing me of the things I didn't do. Like she is entitled to call me names and make me a slave because I am living in her house. She even let her daughter bully me and laugh about it. She always tell her kids to hit me with a pillow while I am sleeping. One time She greeted me happy birthday on facebook but she she also said "I should change my behavior" like she is mad and that I act stupid along with happy birthday. How can I change her behavior?

[Avicenna]

Avoid her as much as you can. Older sisters tend not to think they're wrong.