Hello,
I think the one thing you should do is getting out of her way. Yep that’s right, step back and let the cards fall where they may.
The kids father will deal with them and all involved with your sister need to get to some Alanon meetings.
The sad truth is all the detox centers and helping hand will do NOTHING to help her unless she wants help.
She needs to occupy her time with AA and live a whole new way.
But this is something that you can not help with nor get involved with.
This is her path to do what she may.
You my friend need to take care of yourself. Live YOUR life and do understand that this is hers to deal with.