If you've been that badly let down, in my view it's irreparable. When my mother died when I was 39, my very best friend from childhood basically never spoke to me again. I did try, but she'd reluctantly send one reply and that was it. For the 18 months between my mother dying and me confronting her about her behaviour, I never heard from her, not once. And we had known each other since we were three and been like sisters since we were ten and the teacher sat us next to each other. While I agree that others aren't our support humans, this friend never gave me one kind word or shred of support. In fact, when we did have contact, instigated by me, she was pretty hostile. It was like she hated me because my mother died. And she had been fine up to the point when my mum actually passed. It was the weirdest thing ever. Writing that out makes me wonder if she had actually come to dislike me and did this on purpose - i.e. taking away her friendship at the very moment I needed it most.
Anyway, I did eventually talk to her about it, by email as we lived some way apart by that time. I said what was in my heart, about how much she'd meant to me over the years and how amazed and hurt I was that I had never heard from her after Mum went. I predicted I would get the famous non-apology apology "I'm sorry you feel that way" and that's exactly what she said. Bear in mind that this isn't about some argument - this is about my mum dying!
After she said "I'm sorry you feel that way" I really lost my temper. That was 11 years ago and I have no regrets. Nobody needs someone who can't be there for you at all when the chips are down.
Only you know how badly you've been let down, and if there are any mitigating factors. Mine was especially brutal, calculated you might say, with no mitigating factors at all, but YMMV.
Good luck in sorting it all out in your mind.