You're the better person for having exactly those morals.

It's pretty clear your family treat your sister and you like shit. Any chance either of you could work towards moving out together when you've got more money behind you?

About 10 years ago I knew of a young lady not much older than your sister who moved out and took her much younger sister with her because of similar circumstances. She worked hard to provide for the two of them, getting assistance from a foodbank and the Salvos and friends.

My own two older sisters constantly stole from me as a kid. One even got addicted to drugs and hocked the stuff she stole from me to feed the habit. I don't consider them family now. They never changed. Might have the same blood, but they're not family.