How much $$ is she willing to spend?
I have this lens:
http://www.amazon.com/Tamron-28-75mm...2647687&sr=8-2
I like it because it has a constant f2.8 aperture, which is handy for indoor shots. It's not a macro lens, so I can't get in real close, but that doesn't bother me as I don't take or want to take those shots. It's pretty much on my camera 80% of the time. I really like it.
I'm by no means a photo expert, and amateur would be too generous, but all of the pics on my website were with that lens (on a D40).
The other thing that really helped me is a different flash. I got the SB-400, for $100 its great. I like it because you can bounce the flash, so it gives a much more natural picture w/o the harshness of a direct flash. Most of the pics on my site also used this flash. You don't realize just how crappy the build in flash is until you upgrade.
Had I known then what I know now, the SB-400 would have been my first upgrade to my camera before a lens, just my 2¢. Better lighting can make all of the difference.
Others that might be good:
http://www.amazon.com/Nikon-35mm-AF-...2647768&sr=1-6
http://www.amazon.com/Sigma-70-300mm...2647831&sr=1-8
http://www.amazon.com/Sigma-17-70mm-...647877&sr=1-14