The 450d is a really smart camera and Im sure she will be pleased with it.
Re upgrading, yes they do, all companies release new models, but Canon dont discontinue their models anywhere near as quickly as Nikon and Canon resell better too.
I cant agree on the standard kit lens, I have seen some fabulous shots with it. I have several lenses and my favourite at present is a Sigma 70-200 F/2.8, was around £550 I think, I also use a 1.4x teleconverter on it.
Its not all about the lens, you have to have the camera set right too, get a good bit of glass and know your camera and you will