FWIW,
I'm doing better since my earlier post. I think part of the problem is that cats get into everything so everything reminds you of them when they're gone. It's hard to remember the "it's better to have loved and lost than never to have loved at all" when you are going through the losing part. All and all, I'll keep owning pets as I find that the joy outweighs the sadness.
I also think that the bond is so strong because, unlike most people, they become a part of your daily life and you theirs, even the unglamorous morning rituals, hell - everything. Some time in the future when I stop hurting from this, I'd love to explore the psychology of why I'm so torn up. I think it's pretty obvious but I still feel like making excuses for myself - why I'm acting so silly.
Again, best wishes for your kitty and I'm sorry that she has cancer.