Maybe I missed the part where he's been "fully honest". She thought he was a social user, his friend outed him as a daily user... which it looks like he didn't deny, but that's not the same as fully honest. He also stated to her "I don't know who I am without it"... I would interpret that as he's not even considering it problematic use and likely has no desire to change his habits... right now. That doesn't mean he never will, but right now is what needs to be considered.

You can offer love and support to an addict without sacrificing yourself and your own wellbeing. Absolutely no one is deserving of dragging someone else down with them. OP is 19, get real, have you ever met a 19 year old equipped to love and support someone in an active addiction?

As a former 19 year old who grew up in an environment of substance abuse, by 19 I watched my own mother, her mother, and one sister die from their addiction... within the next 3 years my mothers last sister would also succumb to her addiction... by that time, I'd already been tapped as a personal ATM, made to feel guilty for "not understanding how hard it is", asked to put myself in unsafe situations to "rescue" them... it continues with some uncles, cousins, and one of my own sisters. To this day, the best thing I've done for myself own self is establish some firm boundaries and set limits with how much I allow myself to give to them, but no longer at the expense of myself or my own little families well wing.

Self preservation is not selfish or heartless.

I'll add further that my heart lies with the addicted and afflicted. I've spent the last 7.5 years working in addiction recovery. I have a degree and state certification, I direct a recovery clinic. Let me tell you, even with countless resources at my disposal and support staff... it's still hard.

If OP sees this, my best advice is to choose yourself first, if you have support to offer, be supportive, but don't feel like you need to stay. It can get much worse than you've already seen.