Sometimes

I wonder if I'm a sister or a servant.

For my life, I've been putting up with my sister expecting me to do things for her, and the few times that I stand up for myself and refuse, she calls me a bitch, and then starts calling her friends to complain about me.

But I've decided I've had enough of being treated like a servant.

Today we went grocery shopping because I just started work and wanted to get snacks etc in case I got hungry.

This is what I bought:
1 can of tuna
4 small packs containing 10 tea bags each
1 bag of 3-in-1 coffee mix sticks
3 cup noodles
1 blue tack
1 packet of miso soup

Then she starts saying I've bought too much, and forces me to stop buying, when the trolley is 2/3 her stuff. Of course I accede. Can anyone tell me if the above amount is much? it didn't even fill up one NTUC plastic bag completely.

Afterwards, she has 3 plastic bags, and although its the usual amount people carry, I know its too much for her because she doesn't like carrying stuff, so I ask if we should push the trolley to the shopping centre exit where some people put the trolleys. She says no, its fine. And then when I return the trolley, she demands for me to help carry one for her. I refused, even though it was light, because firstly she didn't even let me do my grocery shopping, secondly I already offered that we bring the trolley to the exit nearest out house, and thirdly she demanded instead of asking nicely. After demanding about four times for me to take it, she finally huffed and took it, and then stormed off (I've never seen her walking that fast in my life).

Subsequently, we got in the lift, I pressed the level, and then when the lift door opened I motioned for her to go out first since she has an unfortunate tendency of suffering lift doors closing on her, but instead she yelled "what now you expect me to open the door too when I have no hands?!" and I was shocked because I let her out of the lift first. And then I open the door and immediately she starts complaining to my mother how I only have one bag to hold but I can't help her hold and dumps her stuff on the hall floor.

I wonder if it is wrong of me to wonder if I'm a servant, because its hard to tell otherwise. Sometimes thank yous and nice requests don't hurt.