Struggling after the loss of my sweet, spicy cat

I lost my soul-cat, Cinnamon, unexpectedly 3 weeks ago. I am still struggling with losing her and replay her death in my head constantly. I am trying to be okay, but I don't know if I ever will.

I knew something was off when she didn't run to greet me when I came home from work the evening before she passed. She slept under the bed the entire night and I was racked with unexplained anxiety that I shrugged off. The next morning, she refused food, didn't respond to my calls or touch, and was limp/weak when I found her under the bed. When I brought her to the vet, the vet was not optimistic, but willing to do whatever I wanted to do to try and help her. She had been diagnosed with FIV 3 years ago, and the doctor believed it had spread to her bone marrow and was causing her to become severely anemic. They also found a mass in her abdomen that they believed was lymphoma. I had just taken her for her annual physical not even a month prior and they didn't see any of this. When I took her to the referred vet, they were willing to hospitalize her and do whatever it took to help. I was about to sign off on the hospitalization and asked to see her first. I knew then that I couldn't hospitalize her. She was my baby and the thought of her passing alone, scared, surrounded by strangers would've eaten me alive. I talked to the vet, and the chances of her recovering at all were slim to none. I would maybe get a couple more days with her.

I made the choice. And I have to live with that decision. I just hope that she understood that I didn't want her to suffer. Or be in pain. Everything I did over the last decade was for her. My brother found her in a dumpster at a few weeks old, and she chose me when I met her. I took her in and gave her the absolute best life I could've. I miss her every single day. I never pictured a life without her, and now that I'm living it, it feels dull and colorless.

I feel numb. I miss her so much. I'm struggling and need support. Did I do the right thing?