silly question what does "D" version mean, better or worst
You question would only be silly if it were not asked. :) The D version transmits the focus distance to the camera for supposedly more accurate metering. Not a big deal, in my opinion. All Nikon meters are very accurate.
that is the part I don't get ? does she want to trade for a D version as this one she has is a non D . I have a 50mm D version .
There is no mention of what is wanted in trade. The lens pictured is the first AF version (note the narrow plastic focus ring), and is a non D. While the image quality of this one is very good, none of Nikon's first AF lenses were popular, which lowers their resale value. For that reason, I think the asking price is much too high.