How to overcome deep relational betrayal?

r/

TL;DR I (26M) ended a relationship with a 31F who I’ve known for nearly 15 years because of an irreparable betrayal wound*. How do I overcome this?

* – Brief mentions of suicide; read with caution.

Earlier this year, my partner (also 26M) suffered a major mental health crisis which resulted in hospitalization. Thankfully, my partner survived without long lasting effects. My 31F friend (we’ll call her F) had created a group chat with a few mutual friends, and only two weeks after this incident occurred, one of these friends of F began sending my partner texts to “kill themselves and make sure the job is finished by shooting for the stars” completely unprompted. This obviously really upset my partner, and when this was expressed, her friend immediately claimed it was “just a joke” while F also defended them. But the thing also, is that I had pre-existing trauma surrounding this topic and already put up a very clear boundary to this group against talking lightly about it; so for this to happen, it felt like a double whammy of disrespect to me and my partner. I tried to explain this to them, and that I could not be friends with anyone who was going to make/defend jokes about suicide, ESPECIALLY directed at my partner, but to my complete shock, F expressed she did not care how long she and I had been friends — she was not going to “pick one side over another because it’s overdramatic to be upset about suicide baiting” and also told me I was “emotionally manipulative” for even trying to talk her about it. It’s been a few weeks since me and my partner have completely cut ties with F and her friends, but I don’t know how to overcome this deep sense of betrayal. I never expected F to act in such a way (we’d had our differences over the years, but I’d never seen this type of cruelty from her) and she was a big part of my life being my longest friend before this. What does moving toward healing look like? I am desperate for advice.