As healthy as my lifestyle seemed, I contracted measles, mumps, rubella, a type of viral meningitis, scarlatina, whooping cough, yearly tonsillitis, and chickenpox, some of which are vaccine preventable. In my twenties I got precancerous HPV and spent 6 months of my life wondering how I was going to tell my two children under the age of 7 that mummy might have cancer before it was safely removed.
That is because pathogens seriously don't care how healthy you are. They evolved specifically to evade the immune system. It also takes around two weeks for the immune system to start producing antibodies, so that the viruses or bacteria have plenty of time to incubate and cause disease before your body can put up defenses. Many pathogens can kill long before the body responds, and antibiotic or antiviral drugs don't work for everything. Vaccination has saved millions of lives, by preventing illness in the first place.
I have to say that the "healthy" lifestyle this woman's mother imposed on her and she is imposing on her children is a lifestyle of deprivation. While other kids got to eat tasty food, she was only allowed boring swill. I think that she is the exception rather than the rule, in maintaining that kind of diet even after reaching adulthood. Lots of people are likely to indulge to the point of obesity, because they never were allowed tasty food as children, and never learned self-control.
I still resent my mother’s home made granola. Having to eat that stuff when I was a hungry 10 year old messed with my mind. Made me want to kill plants as if revenge would improve the taste.