Simply ghost the drive after a full (clean) install, and have her save the important files to a specific directory that you can have task scheduler back up once/day or on bootup if she turns the machine off when she's not using it (my mother leaves hers on all the time).

If she screws something up, nuke the main drive/partition, throw the original image back over it, and everything is good again. Unless she gets something *extremely* militant, it should work perfectly.