I also lost my beautiful orange tabby. When she was a kitten, the vet initially thought she was a boy as most gingers are usually male, so we always thought she was extra special.
She was also my love cat. She loved to be near us - you could even bring her into the bath. I calculated that I put her through 9 moves, poor thing - but she never complained.
I also struggle with immense guilt. I alternate between thinking I should have either never taken her to the vet or taken her a lot more times. I noticed her decline (unfortunately around the beginning of the pandemic so the vet services were not as usual) (but now I think maybe things had started earlier? She had all her teeth removed at 3 so I chalked up some of her digestive issues to not having teeth for most of her adult life). The first visit (which was virtual) they thought maybe IBD, cancer, arthritis... 1 week later in person visit something with her spine, but the vet noted a lot of pain so prescribed pain meds. I don't know if that's what did it. I wish I had researched more or pushed for more diagnostics. I am broken hearted.
I love and miss her so much and thought she had many more years with me. She was so trusting and I feel like I couldn't protect her in her hour of need.
I'm not sure if I'll ever be able to get another orange cat again because I will always be searching her Her. They are so special.