help for my younger sibling?? dont know what to do
trigger warning for self harm mention
I have a younger sibling who has a substance abuse issue, and it seemingly stems from just wanting to escape whatever it is she's feeling. She's been hospitalized twice, was sober for 7 months and now is back to stealing medication etc. It ranges from weed to Benadryl and other things. We have everything locked in safe but she finds things somehow. We don't know how to help her, she refuses any kind of therapy and when we try and restrict her from bedrotting by limiting screen time she threatens to off herself. Shes been in therapy a few times but would never really be honest with the therapist. When she was in an institution she lied so she would be able to leave it sooner, she was rude to the staff and even got written up for telling other patients that if they wanted to leave they should lie too. She usually acts pretty happy around me, when we go out she seems to have a good time, but at home she's just really mopey and sleeps a ton. She overdosed 7 months ago (wasn't purposeful.) and I was the one who found her, it really messed with me. i have a history of self harm and MDD so she's most comfortable talking to me since I can relate in some way, but given I am not entirely stable myself trying to comfort her and support her is becoming really draining and its starting to keep me up at night. I feel anxious all the time worrying about her. She doesn't seem to want to change and when I ask her if she even cares that its not only hurting her wellbeing but also everyone else around her she says no. lecturing/sympathizing/talking with her for hours has done nothing. she doesnt listen, she says she doesnt care. She can be verbally abusive, she often gets into screaming fits with my family. Any attempt at just sitting down and talking with her ends in a meltdown of some form. Ive been told to just leave it be because there's no helping someone who doesn't want any help but shes 15, I couldn't live with myself if something happened to her. My parents don't seem to know what to do, they give her almost anything she asks for.. which i feel is part of the issue. I feel like im the only one who can help.
edit; adding here she has ADHD , shes on medication for that but hates taking it. Shes been on meds for depression but refused to take them after a week.