Quoted:
Go for the Canon 40D. You can get them used for cheap. Probably the best bang for your buck given your application.
+1 The 40D is really a fantastic camera, and the differences are pretty slight in reality compared to the latest and greatest 50D. Plus, the 40D can be found for great prices right now.
Nothing wrong with the Nikons at all, they are wonderful cameras as well. But one thing I think Canon has going for it at this time, is the lenses and especially their prices right now (Nikon did a price hike in the winter). A lot of the "fast" quality lenses of the Nikons are quite a bit more than their counterparts in the Canon models. So for someone that is on a tight budget, but still wants the highest quality they can get (since she does weddings and all), the Canon lenses are really nice.
A very famous wedding photographer, David Ziser (
www.digitalprotalk.com ) used soley the 40D for everything up until the new 5D2 came out last fall. The 40D is a wonderfully capable camera.
I have a 5D2 now, but still use the 40D more often than I thought I would, it's just a great setup.