you’re really not alone, in everything you’re written.
It’s what I’ve written in my letter… even when he was going rehab, on the morning, I confronted him with someone.. he STILL lied. It’s the lies… even when you tell them you will still support them. That comes from guilt and shame at using drugs. My partner told me that his self. And whilst they are using, they will be defensive, turn it round on you to deflect things (it’s your problem), denial, minimising, all this is drug tactics they all use.
Maybe it would help you to go speak to her family, find out the real story. I know there’s two sides to any story but more than one member, if they are all saying the same thing, and they have no reason to lie, it might make the picture clearer for you.