NAH (except the boyfriend, who is def TA).

Honestly, getting involved in something like this is incredibly difficult and delicate for so many reasons. I believe it is great she has a friend and a safety net like you, but as you said, she keeps touching the fire and getting burned. At some point, this is not your problem. This is because in these sorts of toxic relationships, those involved often have to figure out for themselves when they have reached a breaking point, and while outside input may be appreciated, and it may be heard, it may not bectaken into action. If she’s not in any immediate danger, voice your concerns, but unfortunately, don’t expect it to change right away. The drug use and cheating is a major red flag for putting her physical health in danger, and that’s the thing I would tell her as to why she should try to leave. Touching on the abusive aspects could sadly have the opposite of your intended affect, because many people in abusive relationships have a hard time breaking the cycle - even with support, it is a very isolating experience for them.

Also INFO - the way this reads it seems like you maybe wish you had more than a friendship with her? Apologies if I’m being presumptive, but just when you say she’s settling it appears to come from a place of... non platonic intentions? No question this guy is an absolute piece of work, but this is still how it reads to me anyhow. If you do have feelings for her, this further complicates things, because then it brings intent into question. If you don’t, disregard this part of my reply.