What she is worried about is that she has programs that run some peripheral equipment such as her embroidery machines and a paper cutting machine. These programs were designed to run on a Windows computer and the computer controls the machines using the drivers supplied by the equipment manufactures. She also uses Firefox. What does Linux use to access the internet?
If you’re asking which browsers you can use, you may use Firefox, Chrome, or whatever you prefer (except IE).
What version of Windows do the machines’ control software require? You could run Windows in a VM on Linux and have a much more secure setup.
Firefox is Linux, as far as special machines, you never know til you try it. My experience with Linux has been, almost everything works right out of the box without doing anything special, however you could always run windows in virtualbox in Linux for those programs you need windows for, or you could just download the Win7 loader and use it instead of continually trying to activate and register your legit copy. Personally I would give Ubuntu a shot.
It would be an interesting experiment to see if the drivers work through a VM.