For her and anyone else that doesn't have a PC tech in the family that lives close by I highly recommend buying a blank CD or DVD (assuming you have a CD/DVD burner in your computer), downloading one of many "live linux" (google it), and burn it to a disk, just for such an emergency. There are many popular ones to choose from. I recommend Linux Mint or Ubuntu but the most recent versions of both will only fit on a DVD. Knoppix is a long time favorite and still has a "CD" version as well.
A "live linux" CD or DVD (there are ways to install to a USB thumb drive as well) lets you insert the disc into any computer (with a compatible drive... or USB port) and restart the computer "booting" it from the software contained on the disc you made *instead* of the software ("operating system", i.e., windows). This will let you troubleshoot the computer, access the internet, and even access all your files on the broken computer before you do a re-install of windows. It doesn't install anything or change any of your computer settings automatically so it's a good thing to have if you are using a "loaner" computer too. Combined with a blank USB thumb drive you can even save work in progress or retrieve files from a corrupt windows computer.
Linux is NOT windows but most windows users won't find the environment so foreign that they can't find their way around things... About as different as Mac OSX is to windows... different but not so different as to be impossible to use.