I think the sister relationship is an exceedingly challenging one. You two are in competition for resources, in essence, and girls are "subtle" in the way they fight. That is, most brothers I know simply punch and kick each other and are physical. So it's easy to get a handle on. Most sisters I know are emotional in their attacks, so it's harder to defend against, and more likely to keep going on for years and years. I'm not saying boys and girls are innately like that but I think society guides us to be that way. And there are of course always exceptions.
My sister was younger by 2 years so growing up I was always "in charge" of her for better and worse. It means I spent a lot of time looking out for her and taking punishments for her. But it also means she felt like I was always older and got special treatment and so on. She wanted to be equal.
So now as adults we rarely talk with each other. Anything I say, she feels I am being bossy because she sees it through a lens of all those years growing up. I feel frustrated that she is still - at age 40 - upset about me not sharing the piano when I was 13 years old. I don't have a time machine!
I think it's good to choose and appreciate your friends as an adult. Your family is not necessarily made up of people whose morals or life focus or anything else matches yours. It is best to spend your energies in directions you 100% approve of.
It's like supporting a charity. You can support a charity which you feel is 50% OK but 50% very iffy. Or you can look around and find a charity which is 100% what you agree with. Why not support the charity exactly in line with your hopes and dreams?
If you do have to cross paths, treat it as a scientific experiment.