24 and traumatised by losing my mum suddenly. please help

Hello all,

I am 23 and just lost my mum suddenly to bladder cancer that had metastasised to her lungs and kidneys. Before this she had been on holiday, music festivals etc. in very good health and very mobile - only 63.

She went to the GP three weeks ago with a cough and was sent to hospital immediately. I offered to go with her but she said it was nothing serious. (I had seen her four days before for a pub lunch so believed this).

She told me it was pneumonia and they were keeping her in on antibiotics. I was with her 9AM-7:30PM every day for the ten days of her admission. little did I know she had actually been diagnosed with stage 4 cancer immediately, her first day there. 

I spent these days bringing her in food, doing her washing, and sitting by her side. I work remote so would bring my laptop and chat with her. 

on her ninth day of admission, she told me she actually had cancer. I was upset hearing she had cancer but given she was so young and had been so fit and healthy before I thought there would certainly be a treatment plan. I went out into the hospital garden and wailed but felt so certain it would be okay, as my mum was is my absolute best friend and I couldn't see any world where she wouldn't be fine.

the next day I came back to the hospital to see my mum and she seemed in a dramatically worse condition than the day before. she could barely speak and was quite confused. she also hallucinated my dad by the door. as I have no experience with illness thought nothing of this as a nurse said to me she would have ups and downs and that pneumonia could confuse older patients.

I gave her a pedicure, brought her a vimto and we chatted about nothing I can recall. at 5pm I gave my mum a kiss, and went home to eat dinner and my brother got the train to London (we are based in Leeds). I fell asleep on the sofa and was woken up by my partner saying my dad had called crying and we needed to go to the hospital immediately. 

when I got there she was unable to speak and had an awful rattle in her throat. the doctor told me the tumor in her lung was too large and she would pass away that night. at this point I only had a day to even process it was cancer and had thought it was treatable (she was going for a biopsy the next day). 

over the next 6 hours I had to wait to see if my brother could get there on time as he had got back to London by the time we found out she was dying. her condition rapidly declined and she couldn't speak. I tried to comfort her but she was in a lot of pain and I didn't want to let her know she was dying as I know it is her biggest fear. I think constantly about what this was like for her.

By the time my brother got back (6 hours later) she had been given morphine and was more comfortable. she stood up and kissed him which was amazing. after this my only interaction with her made no sense, she kept asking me to "put my hand in the glove" and counting, even drawing numbers on me with biro, which was really distressing and I think has traumatised me. It took me a while to realise that this all meant nothing, in the moment I was hoping it was a message for me.

She died soon after my brother arrived and they took the big tube out of her nose. she did look really beautiful, just like she always did. 

I can't get any of it out of my head. I've been off work but im not doing well. I can't stop thinking about her discomfort dying, how sudden it was, if she knew she was dying. Selfishly, I am also thinking about myself. I feel too young to go through this even though I know some people lose their parents as children. I never once thought id have to get married or have children without my mum. I just feel like my life is ruined. everything I wanted for my life is ruined.

any advice appreciated on how to process a traumatic death would be appreciated.