I haven't even seen Target Disk mode in quite a while, but would starting up the iMac in that mode enable her to use all the apps on that machine?
OTOH, they might just end up running on the laptop, so she wouldn't gain any performance improvements.
Screen Sharing really is the "cat's meow!" And if you're willing to pay for a retail installer of Leopard, wy not grab the 'boxed bundle' Apple is offering for a limited time: Leopard + iLife '09 + iWork '09 for $169 US. Leopard alone is $129 and both the other groups are $79 each. I'm not sure of the dates this bundle is for sale, but I don't think both the iLife and iWork '09 versions are even available yet. You might want to check the specs on those bundles, of course, I think some of them require an Intel cpu and most will need Core Graphics to get all the great graphics effects. But your iBook should handle Leopard with no problem, AFAIK.
Also, be aware that your iBook screen is probably much smaller than the iMac's. That means you'll still not see the entire iMac screen at once, even with Screen Sharing. You can still access all of it, you'll simply see the iMac screen 'auto-scroll' when you reach the edge of it in the window you'll have on your iBook. Screen Sharing works best when you are looking at a smaller screen on a large one. But it really is nice for getting to things on another computer, running them there, moving/deleting files there, just about anything you can if you were physically sitting (or lying!) in front of it. Of course, a real advantage is to be able to show another user exactly how and where to find things or how to perform some kind of action. This can be much less intimidating than standing over the users shoulder! Somehow, my brain doesn't seem to control some else's arms/hands as well as it does mine!
Just 'hang in there' and I'm sure we'll find a way to give you the access to the Macs you want! Even if it requires Neil coming up there and moving furniture!
