I found this post in my draft file. I think I was waiting to post this a little farther from the actual incident when my sister might be more inclined to think it funny rather than insulting. Hopefully now is the time, because here it is:
I work in a hospital. People die. This is stressful. Two weeks ago, two patients of mine died in two consecutive days. This was stressful.
My sister works in retail. People are rude. This is stressful. Last week, my sister says "I had such a hard day, it was so stressful." I reply, "Did someone die?" For some reason, my sister missed the humor in this.