What are your opinions on letting a recovering heroin addict get drunk and smoke weed every now and then?

i’m not even going to try the whole “a friend of a friend thing”.
this girl i grew up with, lived with for 6 years, and love like a sister just came back from rehab several weeks ago for heroin abuse. for a few years we lost touch a bit and i wasnt there for her when she needed me, she got into a huge mess and by the time i found out it was too late. the guilt haunted me the entire time she was away for rehab. now that she is back i am not letting her out of my sight. and the one the time i did, she relapsed.
i am her closest friend and really want her to get better and be able to have fun and get her life back together. now, as a normal 18 year old i like to party and drink and so on, i dont do it often and i am very responsible and have smart friends and a father i can go to for help whenever.
so heres the thing, i want to show my friend that she can have a good time without heroin, and my idea of fun is hanging with friends which we do, but i also think its fun to party and i’m wondering, what do you all think? should i put her in these situations? is it too soon?
she tells me she gets cravings to shoot up which i guess is normal for a drug addict but im scared that if she doesnt find pleasure in a more safe, common form she will relapse again and it will be my fault for not helping her enough.