The worst thing was that she knew she was being irrational
I have some sympathy for people with those fears. If you listen to some of the messages in the media and schools, particularly if you are under about 40, then you could easily get the idea that all food is dangerous unless handled like somewhere between live ammunition and medical waste. You need to be certain of sterile storage, surgically sterile preparation, sterilising cooking and instant disposal of the dangerous waste, or you risk death. They are sold on the idea of all food being risky, and only the most carefully prepared food being anything less than downright dangerous.
In reality, it's bollocks. In the typical modern domestic environment you have to be staggeringly careless with food in order to make yourself ill. Provided you keep food in a fridge most of the time, wash preparation surfaces and tools once in a while with soap and water and cook things at least on the outside, you won't come to much harm. Stuff which is potentially dangerous will taste and look terrible, and it will taste pretty bad long before it will harm you (of course, part of the problem with the obsession with dates is that people don't trust their senses: occasionally you do get food which is in date but off, for various reasons). Butter and cheese can go months past its use by date and be safe, even though it will be pretty unpleasant, and yoghurt will go fizzy and start to push the lid up but still be safe (and certainly OK to cook with). People are obsessed with meat being "fresh", when in reality red beef tastes of nothing and properly hung beef will be dark in colour, brown on the outside.
The main ways to make yourself ill are things that happen in bad commercial catering: keeping stuff warm, but not hot, for extended periods, then refrigerating it in contact with other food, then repeating the process. Provided you don't do that, you won't get ill.
Source: have been cooking for forty years, and have never been ill or made others ill from my own cooking. I know what to be careful around and what you can be wildly cavalier with. Unfortunately, a lot of younger cooks aren't taught that, and they underestimate some risks (in-date supermarket chicken, for example, a pack of which I threw away recently and complained about) while crazily overestimating other risks (out of date dairy, in particular, which is almost always safe).