Can someone please help me understand my mother’s death, please make dua

Assalamu alaikum. I know I shouldn’t be posting like this but I’m grieving and confused and not very knowledgeable about some matters of Islam, so I’m hoping others can share wisdom and comfort. My dear mum passed away a couple of weeks ago in hospital. She was only in her early 50s. She was my closest friend and my guide. Alhamdulillah she was very devoted to Allah (swt) and always spoke about how she looked forward to meeting her Lord. About two weeks before she died she developed pain in her side, so I took her to A&E thinking it might be a gallstone. After scans they found fluid in her abdomen and admitted her. For two weeks they treated her for conditions she didn’t have, and only two days before she died a biopsy showed an aggressive stage 4 sarcoma. Her bowels pushed her diaphragm so high she could barely breathe even on maximum oxygen. She needed constant morphine and we were told to prepare for her to pass. I’m shattered because she seemed fine before all this. I’m shattered because I, her eldest daughter, rushed to the hospital every day from 9am to 9pm to sit with her and watched my favourite person on earth get worse. I begged Allah (swt) to spare her, to give us more time and good news, but she kept declining. When she had strength she would recite Quran. I didn’t get a proper final conversation with her - in the first week I was in denial and focused on caring for her, and I regret not speaking to her more about death. But alhamdulillah she wasn’t afraid to die. I don’t understand why Allah (swt) took her from us. Why He took my dad’s soulmate, my little sister’s mother, a sister and a friend. I know subhanAllah we have no right to question the decree of Allah and that this is Qadr, and I was at peace with that for a while, but these last few days it’s been extremely hard. I see her everywhere, I hear her, I feel her, and it breaks me. Every day that passes feels like a day closer to my own death. I’ll never understand why this trial was placed on my family, but I know trials are part of life. Please make dua for her - may Allah grant all our loved ones Jannah and patience to those left behind. It hurts so much to accept that I will never wake up and see her again. I lived for her in many ways; I studied and worked hard because of her and wanted to give her the world, and now I can’t. Was she meant to die? Was this written for her? Why would Allah let her suffer so much in her final weeks - unable to walk, eat, or speak much? She didn’t eat for two weeks before she died and gradually lost feeling in her legs. I can’t understand why this happened to someone who loved Allah so much. Could her death be related to not looking after her health or to severe stress? After my sister-in-law moved in, her stress worsened and I noticed changes in appetite and energy - I wonder if stress triggered or worsened the illness. Did Allah plan this because of her faults? Did she die because of things she did or didn’t do? I just can’t find peace because I don’t understand. Any advice from those with knowledge of Islam, or simply comforting words and duas, would mean a lot right now. Jazakum Allahu khairan.