Welcome to SR, mister.
Detox is best done under medical supervision. It is very dangerous to try alone, and can be fatal. I don't say this to scare you, but to try to keep your sister safe.
Sadly, it is impossible to help an addict, only they can do that. We can encourage them and cheer them on when they make good choices, but in the end it's up to them. If love could save an addict, not one of us would be here.
The Salvation Army has a free rehab program that many have found very good. If she is willing, this program may also help her on her journey to sobriety.
Make yourself comfortable, take a read around, and you will see that you are not alone here.
I will keep your sister and you in my prayers.
Hugs