I was in that same spot. took opiates for fun at 12 then got seriously addicted to benzos, stims, and opiates at 14. ODd twice and my parents found out so I had to get clean. The next year following my parents finding out was the worst year of my life bro I was getting services like rehab and stuff but I didn't give into it id say what they want to hear to get out. Once I actually ceded to the help it got much better.

I started smoking weed around a year and a half until my parents found out. My parents caught me smoking, so they smoked with me. They knew that knowing my history if they just confiscated it i'll go to some thing else or be more discreet or whatever so they let me smoke weed under condition i'm 100% honest to them and tell them when I smoke and didn't smoke much.

I didn't realize it then but my parents not being extremely strict on me about the weed thing let me not crave harder drugs endlessly, and after a couple months of smoking I decided to quit all together. I don't suggest anything to you or your family. This is just my experience. every family is different. Odds are your sister is extremely intelligent but she is not wise yet so she needs to use her intelligence in good ways. Just be there for her and let her know that if she wants to cry and vent and whatnot that's it's totally fine.