My best friend thinks they deserve to be cheated on TW MENTIONS OF SH AND SUICIDE

So I F (18) and my best friend NB (18) have been best friends since middle school. I’ve seen them go through hell and back and have been there for them through their mother’s passing and met them post the trauma of their father passing. We’ve been pretty close and even dated at some point around 8th grade.

About a year back, they went to the mental hospital to better themselves and met someone 1 1/2 year younger there. Ever since then I don’t even know if that’s my best friend anymore.

They started dating a couple months post meeting and my best friend even admitted to having feelings for them when they had just met, ever since then this person has cheated on them, verbally abused them (called their self harm disgusting), has threatened suicide during confrontations (example: they stole money from a family member and threatened to kill themselves when confronted), and act out in extreme ways such as impulsively starting arguments with anyone that confronts my best friend (including me) and has punched her surroundings when angry.

I can tell this relationship is actively killing my friend, and I’ve told them so many times it’s bad, me and numerous other people have had conversations with them telling them to take a break, asking if they feel they deserve this (they said yes) and they are completely utterly convinced their partner is not the problem. Pre- this relationship my best friend was getting better, it was just a year and a half after there mom had passed and I tried to be as supportive as possible despite their living situation being rough. It feels as if they are almost a shell of who they formerly were and I don’t even see them as the person I knew back then anymore.

We recently hung out and the entire time they where texting their partner, even leaving the area we were in to go into their car and continuously text them even though we hadn’t had a sleepover in over a year. Last time me and my friends invited them to a party my friend has hosted, they texted their partner and sat outside the whole time, the same night telling us they were engaged.

I’m at a total loss, I have given up completely. My friend has been in some crappy relationships before and the same type of scenario did kinda play out but they have never been in a relationship this long, toxic, and intense.

Mind you, their partner has no job, is homeschooled, and my best friend is in college and blows money all the time on them.

Every time I have pointed out how bad this is, how toxic the relationship is and that they have the power to leave, they have agreed and have insisted they care about me and the rest of our friends but I just don’t see it anymore. I know they have this attachment because of trauma but I can’t bare to watch it. It feels like I’m actively watching someone kill themself in-front of me, its pains me and I’ve poured my heart out to them about how i feel.

I’ve already lost an older siblings to suicide in my life and I cannot bare to watch this happen to them, but I can’t find myself but be angry, I don’t feel heard when I speak, I feel as if this whole friendship was some type of joke from how much I cater advice and chances for them to distance from toxic people and they fail to do so every single time. I’ve dealt with this with them since 8th grade and tomorrow I think I’m finally going to cut the cord.

This person was my first relationship, my first best friend, and someone I wanted to have at my partners wedding in the future, but I feel I’m the only one brave enough to actually step up and call not only them out but just the plain fact that their partner is toxic to them. Their partners offer nothing to them while they offer their finances, their home, and their love and affection constantly.

They see each other almost every single weekend and I don’t even see my boyfriend that much and we’ve been together longer, I’ve tried numerous times to tell them this is not love this is obsession and a parasitic type of relationship that can kill them.

I’ve even asked them yesterday, “if they cheated again, would you stay?”

And they replied “yes- well she wouldn’t do that.”

But she’s proven herself to do it repeatedly in past relationships, my friend has even stated they’ve accepted themselves as nothing but a partner to them, not a friend, not a best friend, not even a lover, but a partner.

Do I let them go?