I don't really know enough about their relationship to comment on what he should do. For all I know he's the reason she's using in the first place.
But at some point it has to stop, because it's destructive for both of them. Either she is gonna end up dead and he's to blame or she's gonna end up dead and he's not to blame, it doesn't really matter, it just needs to stop before it continues to escalate to the point of irreparable damage if it hasn't already.
Tell her you can't watch her do this to herself anymore, this relationship has become toxic, and she needs help. Then cut contact but keep a way to get in touch with her. Check in after 3 months.
That's what she wants you to say and what she needs you to do. Drugs kill people, and she doesn't deserve to die. She's trapped in a terrible cycle where she's destroying herself for this fix, and that means the fix itself is broken. He's what's called an enabler. If he wasn't in the picture, would she have someone to meet at the top of a building and threaten to kill herself? {{{Or would I just do it?}}} No, I don't think you would, and if you would then you need a hospital stat. My sister tried to kill herself, I've tried to kill myself, I won't tell you what's right for you, but Allah knows best. And you're into the devil's rock, which is what's driving you to behave so erratically in the first place. If you weren't addicted to this drug you probably wouldn't be as suicidal.
But I'm back into adderall, so I'm one to talk. I understand that people get into drugs because of their experiences {{{Sometimes it's an accident}}} Sometimes yes, but often there are underlying traumas that you're self-medicating with this thing because you're too overwhelmed to admit you have a problem and it doesn't make you broken {{{Yeah it kinda does}}} So if you're broken then I'm broken and Slim's broken and everyone's broken. Being broken is the same state of perfection as the clouds in the sky. But you don't have to break yourself beyond being fixed.
It's the alternating states of broken and fixed that make life so pleasurable. But if you're broken most of the time, the game isn't worth the candle.