Why can't my sister let me be independent?

My parents died when I was in P3, which is 12 years ago. I am the last born. My elder sister, who is the first-born, has raised me like her own daughter. From when I was about 10 years old, she started teaching me housework.

I loved it because we used to work together. Then my sister got married and took me to her marital home. She used to assign me chores and I did them wholeheartedly because my sister paid my fees and bought for me nice things such as trendy clothes.

Then she started having children. My sister would hire maids to do the housework and insisted that I supervise them and look after the children.

Last year, I joined university and want to live my own life. I mentioned my plans and my sister was upset. She said I was ungrateful for all she had done for me, saying with me gone; there was no one to keep an eye on the maids.

I do not want to leave my sister's house without her blessing, yet I feel she is being selfish for not allowing me to live my own life.

What should I do?

Rebecca