I just need to talk to the Internet for a second

I feel so devastated. Not I’m mad or I’m upset devastated, just like a piece of me is missing.
My best friend who is my maid of honour has voluntarily been in hospital for 2 months due to some very intrusive thoughts that got really bad. She is my everything. So much so that the joke between my fiancé her and I is that she is the competition and if it wasn’t for my fiancé, I’d be marrying her. She is my soul person. She dragged me out of some really rough times herself and has just always been the one person in the world who understands me and I her.
My heart is breaking because every day I step closer and closer to one of the most important days of my life and I make more and more decisions that unfortunately she can’t be a part of. I’ve talked it through with her and she doesn’t have the capacity to have much of a part in the planning and celebration due to where she’s at which I completely understand and I just want her to be okay but my heart is hurting. I love her so much and celebrating without her doesn’t feel right. I just want her to be okay but I also want her to be by my side. I know that is something incredibly selfish but I genuinely don’t think I could marry my fiancé without my best friend by my side. Today she called and said that she most likely wouldn’t be able to come to my bachelorette. The bachelorette trip is a Beach House for three days and movies in pyjamas and swimming. Now, I don’t even know if I want to have one.
She just hung up the phone from telling me crying, not because she thought I was mad at her because her heart is hurting as much as mine is, if not more. I love her more than anything else in this world and I just feel so alone right now.
I don’t think I need advice. I think I just needed to put this out into the world and talk into a space where no one knows me, but someone might be able to understand my pain