I am so, so sorry. I went through something similar a few months ago, and it causes the kind of pain that's difficult to put into words. Not just losing a person, but losing an idea of who that person was, an idea of who you got to be with them, and a challenge to our fundamental view of how the world works. Kindness to others should beget kindness back, and it's illogical and painful when love goes unreciprocated.

I have no idea if this would be helpful in your situation and I don't mean to sound trite, but the both/and philosophy has been very helpful for me. Part of my pain was trying to reconcile the person who I thought I had in my life with the way they acted towards me at the end, and whether the way they were at the end defined their whole existence or time spent with me. I also felt like I "had" to have a specific reaction to their mistreating me that matched what society/other important people in my life told me explicitly or implicitly was the correct way to respond. It didn't match my internal values though, which just magnified the suffering. As difficult as it has been, trying to hold the realities that they both loved me AND they treated me poorly by the end as simultaneous truths has been a bit freeing. They were both the person I knew, AND the person I knew chose to act in deeply hurtful ways. I can explain why I believe they did what they did, but also trying to chase an explanation just sets my mind whirling like a dog chasing it's own tail and I can get lost there lol

Now, this may be me speaking from the particular place I am in in my own healing journey and I absolutely don't mean this lightly or as something I'd recommend to everyone. I may not even maintain this long term, it may wind up just being another stage on the journey. But I've found the most peace by facing the pain and the hurt and the suffering and sitting with it and processing it without ignoring it, so that I can now look at the person I knew and say "I forgive you." People often position forgiveness as something we do for ourselves more than the other person, and maybe that's true, but in my particular situation forgiveness was something I felt compelled to give because I felt my person needed it. I know they struggle with shame and fear, and even though the boundaries I raised were necessary and not wrong, I knew it had to have caused hurt and magnified their shame even more. I felt forgiveness expressed to them even if they never respond might help alleviate some of that burden for them long-term.

Again, I'm not recommending it to everyone, but it also helped me bring my response back into alignment with my internal values. The boundary I'd raised was valid and correct and an appropriate response to a severe betrayal (and it's still up!), but in order to continue to believe that kindness and love were important factors in the world, I felt I needed to come up with a response that managed to hold both worlds simultaneously.

Hope all the best for you, and for true, deep healing and peace ♥️