This blame the user bullshit has to end.Honestly, if you worry about viruses, it's your own fault. Period. Either get a different kind of computer. Don't use a computer. Or don't use the internet. Worrying about an event that isn't likely to happen with reasonable precautions is irrational.
Sure zero-days happen that aren't patched yet, but those are rare. Nuclear meltdowns happen to, but I don't worry about it.
My point wasn't that it was her fault for getting a virus. But rather why is she worrying about it on a daily basis? The only sensible rationale is that she's doing something where the risk is relatively high.
And if it is painful to watch her worry about viruses, you should do something. Either get her to do something less risky -- whether its change OSes, stop using the internet, etc... Or get counseling for her. I've just never heard of someone so worried about it, and further never seen anyone in pain due to the irrational worries of computer viruses in a loved one.
And I know I sound like a jerk for saying all of this, but honestly, I think you'd both be much happier with some relatively simple changes in life.