It's nice to see someone interested in Photography. I got into it a few years ago and it is quite expensive, but well worth every penny.
I'm not a big fan of the Nikon D3000. The 55-200 lens is decent. What model Rebel was it? the XS or XSi? I would personally look for a 55-200 for the Canon and skip the D3000. The 55-300 is a large focal range and you can start to see barrel distortion (pin cushioning) and soft edges of the image (falloff) if you are printing large prints. The Tamron 55-200 is a great lens and I prefer it over the Sony 55-200 and it rivals some more expensive Canon lenses, as well. This lens can sometimes be found for under $200 or as little as $150.
I personally don't shoot JPEGS too often so in camera editing isn't worth anything to me. Many of the features are for first time users moving up from a Point and Shoot. I mainly shoot RAW and convert them to JPEG or TIFF. Don't let the in camera editing be a selling point. However, I think it is important for her to get to know the camera. Shooting JPEGS from the camera and adjusting the white balance, ISO, and manually setting the Aperture and/or Shutter Speed will give her a much better understanding of the camera and will help her shoot better pictures. Also, RAW will give you better image quality than shooting JPEGS straight from the camera. Sometimes the difference is negligible, but it is nice to know you are using the camera to it's fullest potential.
I'm actually currently selling my camera to do an upgrade. Here are some pics I have taken http://www.dpreview.com/galleries/2391710214/photos
The Rebel XS and the Sony A200 I have are both 10MP and very comparable in Image Quality. I would urge you to skip the D3000 and move up to the D5000 if you really want a Nikon. The D60 is also a very good camera which shares the same 10 MP Image Sensor as my camera.
I think I covered everything, and if I didn't, let me know and I'll explain a little more.