Good morning, PlentyGood! I am sorry to hear that your sister still struggles, still continues that cycle. I understand your frustration. I know how awful it feels to know how unpleasant we can become due to our frustration with someone else's drinking and drugging.
My stepson has been through a couple of hospital/detox/rehab situations, too, and yet still drinks and drugs to this day. So, I get it. When my husband was still alive, we just tried to hope for the best but plan for the worst...with absolutely no expectations.
Sending hugs and prayers for you, your folks, and your sister!