You would have to use a crappy 15' monitor. I think that ruins it. Also, Apple customized this insides of those extensively--it will be very difficult to work with. If you are really adventurous and wanted to try it for her I would get one of the third generation imac (the graphite or/funny blue pattern ones).
You are better off making a fishtank out of an imac (I know that that has been done a few times). A rebuild is possible, but still relatively difficult with a Mac Pro or the Mac Cube if you really want to make a hackintosh.
like what was said before it is possible deppenting on how deep you wish to go the only problem i am having on mine is how to mod a video port from external to internal so i dont have to run my video cable outside the case