You write beautifully and convey your agony well. I'm sorry you're suffering such a horrible cruelty of fate. There is no inherent fairness or justice to the world, and there is certainly nothing that you could have done to have caused her cancer. Cancer is something that just happens to some people. Genetics, bad luck, environmental factors outside our control, and a whole bunch of ???????UNKNOWNS???????? are responsible. Not burnt food. Not a doughnut here or there. Not frozen food.
There's a tendency when disaster happens to try to wonder what we could have done to prevent it. The psychological reason is to feel some sense of control and think "well, it won't happen again". It's a protective thing. It's irrational, because it already happened, but humans are deeply irrational creatures and it comes out of our survival mechanisms.
The anger and bitterness you feel are natural feelings and I hope you do not judge yourself for them. It's not disgusting for you to feel the way you're feeling. Grief is a monster. Grief is horrible torture, and I've seen and lived firsthand what it can do to people. It can torture people into being angry and bitter and hateful. It can break people of everything they believe, because the most important thing of all is for the pain to end. Torture breaks people, and make no mistake, the agony of grief and loss is torture.
If you're able to find therapy, you may benefit from it. If you're able to access a grief support group, you may benefit from one. I briefly went to this grief support group before I had a time conflict come up and they seemed good. It was surprisingly helpful. One thing that was good about it was that it is peer led instead of having a system, so people can speak more freely about their struggles without worrying about getting narcd on: https://kivacenters.org/online-peer-support/, they've got a Living with Loss support group. They're based in Massachussets time so I think that's eastern time in the US.
I'm sorry, comrade. This life is not fair.
Fingers crossed Bad Hasbara does an episode on how bad her take was