Put a fresh install of PC Linux OS on the computer. It is free/ simmilar to the workings of Apple, tho not a commercial product as it is open source. PCLOS with KDE looks very simmilar in design and function to windows. As long as she does not need any windows based software, it would be perfect. Even if she needed a windows based program, WINE runs a lot of them, and for those that don't run, there is usually a linux alternitive