Kissinger, Anne not replying to someone who sent her a letter whilst she was undergoing cancer treatment isn't something I'd condemn her for, though each to their own opinion. I've had cancer. The treatment is as awful as you expect it to be and then worse. You face the fact that one day you'll die. We all know that, but cancer doesn't half focus the mind on mortality. You have to focus on yourself, not other people.
During my treatment, I had to be signed off work by my GP. Walking out the surgery one day, a woman held a door open for me. I didn't say thank you. The woman spoke sarcastically to her child about awful people who don't say thank you. I couldn't be bothered to respond, as I was suffering the after effects of chemotherapy at the time. I briefly thought though that if that's the worst thing that's happened to you, you should be thankful. The reason I didn't say thank you by the way was that I was in shock. There's a lot of shock/fear going round your head when having cancer treatment. What made this particular occasion worse, was my GP told me about his wife, who'd died of the same cancer I was being treated for.